Guide To Crystal maiden

Guide to Rylai Crestfall, Crystal Maiden
Updated for DotA 6.66b

While Maiden is not as strong as she used to be before the nerf to her aura she's still a good hero that works wonders in the right line up. Her aura is invaluable to the entire team early game, she has a nice disable, a slow that works exceptionally well with just 1 skill point and an ultimate that has the potential to do a lot of damage. She can make a team win all her lanes while still providing wards, being a great ganker and adding good AoE in team fights.
The reason I'm writing this guide is that even though she's a fairly easy hero to play I still see decent players use her plain wrong on a regular basis.
It's my first guide and the only plan I had in mind while writing it was to teach people how to play Crystal Maiden so please excuse the rather chaotic format
One last thing: This guide is geared towards somewhat experienced players. That doesn't mean you have to be pro or anything but I'm going to assume you're playing anywhere above pub level so that playing a support hero that gets a chicken and wards for the team actually pays off. You might even do well with this kind of build in a public game if you get people to listen to you and gank but that is definitely not going to happen every game.

Hero Statistics

Notes:
Those are the stats of a fragile caster. As you can see though, while her damage and attack animation are nothing to brag about they're not much worse than those of most casters. Some people on these forums act like last hitting, denying and harassing with CM are close to impossible which is simply wrong.
One thing that does stand out though is her cast animation or rather the back swing of it which is a whopping 2.4 seconds. This means that you only take 0.3 seconds to actually cast a spell but afterwards maiden stands there doing nothing but waving her wand through the air for 2.4 seconds. You should always cancel that part of the animation, as soon as you see Crystal Nova or Frost Bite being cast just order another command right away, don't waste time.

Hero Abilities

Notes:

• Damage type: magical
• Will slow the affected units' movespeed by 30% and attack speed by 20%. This slow does not stack with other frost based slows (Freezing Field, Skadi, Shiva's, Frost Nova, Frost Armour, Chain Frost, Dual Breath, Elder Dragon Form level 3 and itself).
• The maximum range at which you can hit a target is 1100 (700 cast range + 400 AoE).
  Here is a picture to demonstrate how far this is:
  
  This image has been resized. Click this bar to view the full image. The original image is sized 1024x768.

  
• Even though the animation suggests the opposite the damage and slow is applied the instant the spell is cast (similar to quill spray).
• Does not aggro creeps.

A great slow on early levels that turns into a decent source of AoE damage later. Its range is outstanding.

Notes:

• Damage type: magical
• The overall damage is 140/140/210/210 as it deals 70 at the beginning of every second the spell is on the target.
• Renders the target impossible to move or attack.
• Sends a stop command to the target which acts like a mini stun by cancelling the last action of the hero (including channelling spells and tp scrolls)
• If a unit affected by Frost Bite goes invisible you can still see it until Frost Bite wears off.
• Can be dispelled by BKB, Purge, Manta, Mirror Image, Phantasm, Blade Fury, Rage, Time Lapse, Aphotic Shield and Repel
• Blink- and Metarmophosis-based skills cannot be used while under the effect of Frostbite. Those are Blink (AM and QoP), Teleport, Metamorphosis, True Form, Elder Dragon Form, Firefly, Berserker Rage, Split Shot, Shape Shift, Phase Shift, Spirit Form, Flesh Golem, Chemical Rage and Burrow (Scarabs).
• Can't be used on flying unit's (Batrider in Firefly mode), it does work on hovering unit's (Viper, Visage, OD, Batrider without Firefly) though.
• When a hovering unit dies while under the effect of Frost Bite it is stuck in the ground for the rest of the game. In the case of Batrider that means that he permanently loses flying vision during Firefly.
• Lasts 10 seconds on creeps level 5 or lower. This includes lane creeps, most neutral creeps and summons, even the fountain but not Sylla's Spirit Bear and Roshan.

Frost Bite is a great disable which is very useful during the entire game. It lasts longer and does more damage on early levels than similar spells but in return it only prevents few spells from being cast and the damage doesn't increase by much.

Notes:

• Stacks with the Brilliance Aura given by Ring of Basillus.
• The bonus mana regeneration is not considered for percentage mana regeneration increases.

Brilliance Aura is among the most useful abilities in the game. It makes your allies win their lanes without you even needing to gank (and I'm not saying you shouldn't)!

Notes:

• (**) Total area of effect of the spell.
• (***) Area of effect of each explosion.
• Damage type: magical
• The slow is applied on all enemy units within an AoE of 635, even if they aren't hit by any explosion (lasts 1 second).
  Just like Crystal Nova Freezing Field slows movement speed by 30% and attack speed by 20% and again, it does not stack with any other frost based slows.
• Every 0.1 seconds one explosion is made, for a total of 40 explosions.
• Can be improved by Aghanim's Scepter (* shows the improved values).

Freezing Field is a rather situational Ultimate. Under the right circumstances it has the potential to wreak havok but often it's cancelled early.

Skill Build

Level 1 - Frost Bite
Level 2 - Brilliance Aura/Crystal Nova
Level 3 - Brilliance Aura
Level 4 - Crystal Nova/Brilliance Aura
Level 5 - Brilliance Aura
Level 6 - Freezing Field
Level 7 - Brilliance Aura
Level 8-10 - Frost Bite
Level 11 - Freezing Field
Level 12-14 - Crystal Nova
Level 15 - Attribute Bonus
Level 16 - Freezing Field
Level 17-25 - Attribute Bonuses

Justification: Frost Bite on level 1 is a no brainer, great disable and nice to harass with. After that Aura is maxed, it's simply her best skill. You should get one level of Crystal Nova for the slow though, it stays the same on all levels, then Bite is maxed, then Nova for the damage. Freezing Field whenever possible for some nice AoE.


Variations:

• Depending on how aggressive your lane is you can get Nova at any time between levels 2 and 4. Say if you're laning with Juggernaut go for the level 2 Nova and see if you can get first blood, if for some reason you're laning with say Tide you might want to get aura earlier to help out the rest of your team more.
• In a few lanes having a few points in Bite rather early is fairly important, such as CM+Admiral. In that lane I might go Bite, Aura, Bite, Aura, Aura, Nova, Aura, then continue just like the normal build.
  Another situation when levelling Frost Bite earlier can be a good idea is when laning against an Anti Mage or Queen of Pain. Depending on how well your team can utilize Brilliance Aura you could even max it first if that means you will win your lane.
• If you're going for an instant first blood with 3-4 heroes (and only then!) you can go for Nova first. The slow allows you to get in more hits than the low level frost bite would. In any other cases Frost Bite is far superior (as to why read the Q&A section below).
• If you don't like maxing Nova you don't have to, I do think though that it's best to max it. Some people tend to get stats when they die too fast but that's just silly. I mean do you think 78 hp is going to help, with Maiden's crappy armour? Better get those extra levels of Nova so you can deal some burst damage before you die.
• Sometimes it's better to skill Freezing Field a bit later (read the Q&A section below).

Skill build Q&A:

• Q: Don't you have too little mana with that build?
  A: With 3 gg branches (or a Wand) you only won’t have enough mana to cast all your spells at the same time on levels 6 and 16. At level 6 you need about 5 seconds between the first and the last spell, level 16 you need about 2 seconds. With a charge on your wand/stick you’re good anytime.
• Q: Why do you get your ultimate at level 6?
  A: I used to delay it myself but let’s face it: If you don’t get your ultimate that’s one level more of Frost Bite; half a second disabling time and at level 8 (and only at level 8) 70 damage. If you ask me simply having the option to cast your ultimate is a lot more valuable than that.
  Yes, casting Bite three times and Nova twice is more efficient than casting Bite, Nova and Freezing Field but it also requires the battle to last for 30 seconds, you need to stay alive and in range to cast your spells for the entire time. This doesn't happen a lot and when it does and you went for Freezing Field you can still do that, again, it's about the option to cast Freezing Field, skilling it doesn't mean you have to use it when there's no good opportunity.
  If you can not farm at least 3 branches or a magic stick (boots become more important at some point and so are wards) then skill your ultimate a bit later. This should be very rare though as gg branches are extremely cheap.
• Q: But don't all pros skip Freezing Field until later in the game?
  A: No. This is a common misconception. In the making of this guide I ran a lot of pro replays through parsers and there were hardly any players that didn't level Freezing Field at level 6. People do have different skill builds with Maiden but I believe the skill build I listed above is the best; it's also the most common among pro players.
• Q: Shouldn't you get Frost Nova at level 1?
  A: The slow from Frost Nova allows you to get in a lot more hits when you’re chasing than level 1 Frost Bite does. Thus, as mentioned above, if you’re trying to get first blood right away (which is often done in competitive games) yes, Frost Nova is superior there. For laning however Frost Bite beats Frost Nova by far. Sure, you might think now that you can land more hits on the slowed target than with Frost Bite but in reality there will be creeps and usually another hero which will definitely attack you when you’re trying to chase someone for 5 seconds in the lane. Frost Bite is far more useful here as it renders the target immobile so you don’t have to charge into enemy creeps. It also deals 60 more damage at level 1. That easily makes up for Frost Nova's AoE.
  So yes, Frost Nova is better for killing but Frost Bite is simply better for wearing your enemies down which is what you will be doing on level 1 most of the time, then, when they're low you can use Frost Nova to try to get a kill.

Item Build

Starting Items

+


Always get a chicken. Don't be a douche bag, just do it, chances are the rest of your team needs the money more than you do.
If you have to buy wards right away because noone else is going to well then again just do it, it's all for the greater good. Since you won't have much money left I suggest getting a set of tangos and a couple of gg branches, if you need regen after that just use the chicken.
If there's another hero that can buy the first set of wards (and there should be in most games) I suggest you get the items listed above. If you know that you'll be harassed a lot and/or like playing very aggressively you can get an extra healing salve or set of tangos instead of 2 branches. Sometimes starting with a magic stick might also be a good idea, for example if you're laning against a Zeus or Bristle Back.
Another thing I sometimes do is buying tangos for another hero. When we use a Centaur+CM lane in a clan war for example Centaur usually starts off with a stout shield, a quelling blade and a flask and I pass him a set of tangos. That way we don’t have to pass the tangos back and forth all the time. It’s a pretty situational thing though.

If you'd like to go for a different combination of items that's fine, just make sure your team has a chicken and a set of wards.

Core Items

+


In most games the first thing you should do once you get 200 gold is upgrading the chicken. Having a crow is simply much better since it's faster and items in a crow are actually safe; I'm pretty sure you'll never see a decent player use a chicken to buy his Sacred Relic from the secret shop. It's always useful, for your team as well as yourself, so you don't have to walk back to the base every time you want to buy a new set of wards.
Around the 6 minute mark your first couple of wards will run out and you will definitely want to replace those. If you can afford it also start counter warding, especially when you know where your enemies have their wards.
The first real item you should buy for yourself are boots. Most heroes get some other items like bracers first but since you're playing support that would delay your boots by too much, you need them for ganking and escaping ganks.
Also grab a tp scroll and keep one for the rest of the game. Crystal Maiden is great for so called "save TPs". Basically anytime an enemy decides to tower dive to kill one of your allies you should tp there as fast as possible and freeze him in tower range. This will often save your ally as well as giving you a good chance to get a kill so always look out for those opportunities. (There are of course situations when you can not save your ally and you'll only suicide in the process, in that case you obviously shouldn't tp.)
Next you should get a Magic Wand. You can get the parts earlier, both Magic Stick and gg branches are great for their price but getting Boots is usually more important than completing the Wand. This means that you might have to (temporarily) drop or sell a gg branch but really, it's not a huge loss.
If needed you can also use the crow to get some regen (tangos or flasks) for both you and your lane mate. Sometimes it is smarter to simply go back to the fountain to heal though, I trust you can make that decision.
The last item I listed as "core" is Urn of Shadows and this item is simply amazing. It provides some survivability, comes in small parts but most importantly it has an incredible active ability that is invaluable when pushing but also great during and after ganks. Many people tend to skip this item when someone else has it already but due to the long cool down I actually think having two per team is ideal, three is still okay. If three of your team mates have it already though you should probably skip it and get a bracer or point booster instead.

Luxury Items

Before I start listing items I just want to make sure the following is clear to everyone: The items listed above really are Crystal Maiden's core items. This might seem to be a very cheap core build but please consider that Maiden will hardly ever get to farm, shouldn't really take any kills from other players and will probably die a lot. Also wards are not a one time investment, they should be bought over and over again to provide map control. When playing Crystal Maiden you might well find yourself walking around with this core build for the entire game, this does not mean you're playing badly, more like the opposite.
Thus, when thinking about further items for Crystal Maiden we have to consider a couple of things: Firstly they should be easy to farm, secondly Crystal Maiden does not have a lot of item slots left over. This is the reason bracers are not usually included in my build and should only be bought if the game goes horribly wrong!
Now, without further ado:

Strength Treads
Treads might seem like a horrible investment at first; the attack speed boost is completely useless and for 50 gold more you could get an Ogre Axe which can be used in a BKB or Aghanim’s. But they have one big advantage: They don’t take up an extra slot and as I mentioned before you won’t have a lot of those left over. Most pros have actually started getting strength treads on Maiden in 6.64, by now phase boots are a decent alternative again though.

Phase Boots
Phase boots are pretty great for getting in range to cast your spells and provide some survivability due to the bonus ms. They're not as good as the old phase boots obviously - armour was far better for Maiden than the extra damage is - but the extra mobility is pretty nice and they come in small pieces.

Point Booster
Point Booster is a very cost efficient item that solves your mana issues and provides some much needed survivability. It’s basically like getting a bracer and a null, just that it requires only one slot which makes it far superior. It is harder to farm for but it's worth it.

Kelen's Dagger
Dagger is great for setting up ganks as well as positioning yourself for a nice ultimate in team fights.
It is usually a good choice if you can somehow farm it very early in the game as it helps your ganking a lot. It’s definitely the best choice of luxury items if someone else on your team is warding for some reason. It doesn't exactly solve your mana issues though consider leaving Nova at level 1 for a while when going for a Dagger.

Black King Bar
BKB is obviously gotten to prevent your opponents from cancelling your ultimate right away. Personally I find it a bit overrated; Freezing Field only lasts a maximum of four seconds anyways and with some good positioning or just a good AoE disable by your team (Ravage, Black Hole) I find it rather unnecessary, especially for the cost. I know a lot of people will disagree here though and if you find yourself being stunned the second you cast your ultimate every time and with a lot of cash on your hands then you should definitely consider it. I also recommend getting it when you have a Pit Lord or Treant Protector on your team as they can stop your enemies from moving and attacking but not from throwing their stuns at you. Ogre Axe being a part of the recipe is fairly nice.

Aghanim's Scepter
Let’s face it; the biggest reason to get this is that it requires a Point Booster which you will probably have already. The stats are decent but the boost to your ultimate isn’t overwhelming. Still, it’s okay when you can land your ultimates consistently (again, Black Hole, Ravage and the like are your friends) but generally there are better items.

Mekansm
Mekansm is a good support item for Crystal Maiden, it just has two disadvantages: Unlike any of the 3 items above it will not help you with your ultimate and it also costs some mana while not increasing your mana pool.
Thus it is best in games when you can not land your ultimate and a BKB will not change this (for example when an enemy Naga always saves her net for you). Either get a Point Booster first or only get one level of Nova when going for Mekansm.

Ghost Scepter
Ghost Scepter is a vastly underrated, yet very, very situational item. Its purpose is to counter well farmed physical damage carries late game when they can kill a support hero like Crystal Maiden with just a few hits.
On the other hand it also makes you very susceptible to nukes thus you have to think carefully about when to buy and use it.

Necronomicon
Necronomicon is obviously a great counter for invisible heroes or heroes with small mana pools that are very reliant on their mana (Leoric, refresher Tide or Treant) and works rather well in Push strats.
However Neconomicon is most effective when you can farm it fast and it doesn't help with Crystal Maiden's ultimate at all thus you should only get it in rather extreme situations, usually there are better Necronomicon carriers on your team.

Boots of Travel
Mobility is extremely important in DotA, especially towards late game when a single push can end the game. Now CM is not exactly the type of hero that after a won team battle can TP to the other side of the map and single handedly take down a tower and a couple of barracks but she can help do so at least. You should only get this very late into the game though; BoT shouldn’t be your first luxury item.

Guinsoo's Scythe of Vyse
Okay, now this is a super, super, super luxury item. I’m pretty sure if you play CM as ward bitch map control technician you will be able to farm this in less than 1% of your games (not counting stomps) but if you can it’s extremely powerful, especially late game.

Again, in most games you will probably end up with your core, treads and a point booster but it's far better to play Crystal Maiden as a true supporter and ending up with few items than aiming for all those big shiny items and taking farm from heroes that need it more than you.

Playing Crystal Maiden

Laning

Lane Partners
The amount of heroes that Crystal Maiden can form strong lanes with is incredible and only matched by very few heroes. Here are some examples:

Note that many more are possible, being a ranged hero that doesn't need much farm and has a targeted disable means she can lane with almost any hero in the game, she works very well in tri lanes as well.

Why not to solo
I generally discourage soloing CM. It's not that she wasn't able to do it at all, she's got 600 range, nova which she can use to farm and a disable that can save her life if need be but she still remains a weak solo, mostly due to her attack animation. And why would you want to solo such a great dual laner anyways? I've heard some people say that getting her aura even earlier will help the rest of the team even more but you always have to consider if that is worth giving an enemy hero easy farm while one of your heroes gets less experience because the solo lane is occupied. The answer to that will pretty much always be no.

How to play in dual lanes
When you get to your lane be aggressive. You have 600 range, go make use of that, harass some. Don't be afraid to spam Bite, it only costs 115 mana and you have aura but always save the mana for one Bite in case you get into trouble. Also make sure that whenever you cast it you follow up with at least one hit on that enemy so you're actually doing some damage. When you feel like you can get a kill go for it and use Frost Nova as well, just make sure you make good use of the slow, don't just cast Nova right after Bite, instead cast it when Bite has worn off.
Also always look for lanes to gank. Especially when you’re laning with a hero like Sniper who is able to hold the lane by himself for a while you should keep your eyes open for an opportunity to gank. Maybe your enemies pushed to far, or they’re low, maybe there’s an invisibility or haste rune.
When you’re laning with a melee hero that can’t farm too well without you being there I suggest you go ganking after killing one of your opponents. That makes it easier on your ally to farm, especially if your enemy thinks you’re just going around the trees to sneak up on him.
As far as creeps are concerned focus on denying and harassing, leave the last hits to your lane partner (if he can't get them feel free to take them of course).

About tri lanes
Playing Crystal Maiden in a tri lane is similar to playing her in a dual lane, except that you can be even more aggressive.
You should probably go for first blood right away, hide somewhere behind the trees and surprise your enemies from behind once you see them.
After that, depending on the game you have to decide if you want to permanently keep your opponents away from creeps (this may sound extreme but it's possible with allies like VS and Sven) or if you would rather gank more and get some kills. Most of the time the latter is better so you don't lose your other lanes. Tri lanes usually consist of one hero that can make good use of the farm (Sven, Slardar, Naix, Kunkka) and two strong item independent gankers (Maiden is one of those). After creating a decent advantage for your carry in the first few minutes you and your ganker buddy should start roaming in between lanes. Make sure though that your opponents do not have a ward between the tri lane and the mid lane, they should never feel completely save.

Roaming
For those who don't know: A "roaming" hero is one that doesn't have a definite lane, instead he choses to switch between lanes constantly, attempting to get kills wherever he goes with the help of the heroes that already are in the lane.
Crystal Maiden is a good roamer but be warned: Roaming does not work in just any line up. You at least need a strong dual lane as well as one solo hero with strong offensive capabilities (SF or Tinker work well), otherwise you will just walk from lane to lane without ever killing anyone.
Basically roaming is very similar to tri laning: You start off with your dual lane, you skill Nova first and try an instant first blood. After that you leave the lane and either go to mid lane (where your strong solo should be positioned) or come back in case the enemy heroes in the lane that's up against your dual lane are too careless. Keep alternating between the lanes but never go to a lane where you can't land a kill (for example if you have a solo Treant that is not level 6 yet or doesn't have his ultimate don't waste your time).

Ganking
As Crystal Maiden your role is typically to initiate the ganks. If you can get in Bite range then you should Bite your enemy first and use Nova once Bite has worn off, otherwise use Nova to get into Range. Depending on the situation you can sometimes wait the entire 5 seconds before you Bite your enemy, often you will want to use Bite earlier though to prevent your enemy from running to his tower for example.
If you can get off a good freezing field then go for it. Many people think this spell is only good in team battles but let’s face it, in most team battles you get stunned and focused down anyways, Freezing Field is not like Black Hole or Overgrowth, the cool down isn’t as long and it’s just not as valuable. If it can get you a kill then go for it.

Team Battles
Team battles are definitely the most complicated part of DotA thus it’s hard for me to give you any specific advice here. If you can, then try to get in a good ultimate. This can be very easy at times, especially with a Tide or Enigma on your team or when you somehow managed to farm a Dagger + BKB. In other games it will be close to impossible. When your enemies have mass stuns while your allies have very little it becomes difficult. Just remember that if you stay alive and Bite and Nova repeatedly you’ll be far more of a help to your team than if you run in, cast a crappy Freezing Field for a second, then die. The gold you lose from dying is not so important, not being there to disable enemies however is. Thus you shouldn’t be too afraid of death; if you can land a good ultimate but you’ll die in the process then go for it. But charging in thinking “doesn’t matter if I die” isn’t a smart thing to do.
Also as with many other heroes always make sure you cast all your spells before you die, in team battles that usually means Nova first, run in, Bite, Freezing Field but really, it all depends on the situation.

Farming
As mentioned before Crystal Maiden should not farm much. She is one of the heroes that work fairly well with close to no farm, thus it is better to leave creeps to your allies most of the time. There will be situations though when there is little else to do. After a team battle in which all of your allies either died or lost so much HP that they have to go heal at the fountain for example you can not gank and there is no one else to take the farm so farming yourself is perfectly fine.
Interestingly CM, a hero that should take so little farm, has 3 spells that help her do so:

• Crystal Nova can often be used to get a couple of creeps as well as lowering the other creeps' HP so you can defend, push or just simply farm faster. I don't mean spam it all game long but when you don't need Nova for a second and there's a low hp creep or two around you can just use Nova to last hit it provided you can spare the mana. While CM's attack animation isn't as bad as everyone claims (it's pretty damn good for harassing actually) it does kind of blow when it comes to last hitting.
• Frost Bite is particularly good to kill neutral creeps. As mentioned before no matter how many skill points you put into it, it will always last 10 seconds on creeps that are level 5 or below, that's 700 damage! This means it will kill all creeps below level 4 and do significant damage to level 5 creeps.
  When using Frost Bite to farm you have to be sure there are no enemies nearby. Crystal Maiden is an easy kill anyways, take away her only disable and she becomes food for most enemies.
• Using Freezing Field on creeps might seem silly but in certain situations it's actually a good idea. Let's take the following scenario: Your team has just killed several opponents in the forest and now wants to push mid lane. There is a huge creep wave outside your base top lane though that will push down your tower and barracks if you don't stop it. Now in most low level games the carry will probably shout "I'll def" acting like he just made a huge sacrifice when in reality he just wants to farm. And hey, farm for your carry is good right? True, but let's assume your enemies actually seem to be winning this game, say their carry is getting too strong and you just managed to take him out. This is your chance to push. Well, then Maiden should TP. She's pretty worthless when it comes to taking down buildings anyways and with her ultimate she can stop a creep wave just like a carry could, maybe even faster.

Using Freezing Field correctly
There are two key factors that decide whether your Freezing Field is successful: Positioning and Timing. Basically you want to hit as many opponents as possible but even more importantly you don't want to be interrupted. There are 4 ways to accomplish this:

• BKB/Repel
  This is probably the easiest way not to get interrupted. Just activate your BKB before you cast your ultimate. There are some abilities that go through BKB (Bash, Pit of Malice and a whole lot of Ultimates come to mind) but when playing against those heroes you should think twice about getting that BKB anyways.
• Using your allies' disables
  Global Silence, Ravage, Black Hole, Reverse Polarity and similar spells can all help you greatly in landing a good ultimate and making sure you can't be disabled. The best part is that many of those also ensure that you can not even get beaten to death plus noone can run from you. Thus, if you have a hero with some big disable on your team always wait for him to initiate, then blink/walk in and cast your ultimate.
• Positioning
  Basically by hiding behind a tree or up a ramp or cliff you can break the line of sight between yourself and your enemy. Many stuns in DotA are targeted, your ultimate isn't. Thus you can still cast it while they can't stop you.
  A little example:
  
  Bad positioning: I'm right next to two stunners. In this scene WD stunned me about a second after I started channeling and they beat me to death. (Casting my ultimate there was a very desperate attempt to escape.)
  

  This image has been resized. Click this bar to view the full image. The original image is sized 1024x768.

  
  Cookie to whoever can tell me why there's Sven's face instead of Maiden's, this is not photoshopped.
  
  
  Good positioning: Since I'm up on the cliff my enemies don't have vision of me. Thus neither Rhasta nor Sven or Alchemist can stop me from channelling, yet I'm still able to damage them.
  
• Timing
  This is extremely important in ganks. Sometimes you just have to wait a second until all your enemies have cast their disables, then you can go in and channel away.
  Doesn't require any big items or great allies, just an open eye for all enemies and the spells they cast. It gets problematic in bigger fights though, especially when your enemies have low cool down (mini) stuns like Lightning Bolt, Hellfire Blast or Slithereen Crush.

Warding
Warding is key in any decent level game. It helps your team in ganking, avoiding ganks, getting runes, picking the right battles and even in battles because you can have vision of opponents you wouldn't usually see.
As CM your job is to provide wards for the team. And the oh so popular "bought wards, they're on the chicken" doesn't cut it, you also need to place them.
I could probably also write a guide about warding but luckily others have done that already, so I'll just recommend you take a good look at this guide, it is very well done and covers most important ward spots.
The key here, besides knowing all the ward spots, is to be smart. Predict where the game is going and where wards are needed the most. Sometimes you might not need wards at all (usually when either team desperately tries to push the enemy base, though a ward in the enemy base can be very nice, especially if you have a Pudge or similar on your team).
Also note that during mid and late game you can use the crow for warding when you run out of item slots. Obviously the crow can not place wards anymore but it can still bring you wards, you pass another item on to the crow for a second, place the ward, give the remaining wards back to the crow and take your item again. This should not be done early game though because the crow is usually in high demand during the laning phase.

Overall/Random Tips

Always watch your positioning
Positioning is one of the most important things in DotA. Good positioning wins games, bad positioning loses them very fast.
With a fragile hero like Crystal Maiden it's especially crucial. Fighting at the front of a team battle will get you killed about as fast as a Furion trying to heal at the wrong fountain. Unless you're trying to cast Freezing Field stay back and cast your spells from a save distance.

Stay with your team
Crystal Maiden is a team player. She's hardly a force to be reckoned with; unless you get very lucky with her ultimate she can hardly take a hero 1 on 1. Thus, especially as the game progresses it becomes extremely important that you stick with your team. There will be times when you have to go alone, for warding for example. Try staying out of fights for that time; again, chances are you're not going to win them.

About Frost Bite...
Okay, this might seem pretty random but remember how I mentioned Frost Bite having that stop command when you cast it? Well, Frost Bite itself may not prevent people from casting spells or channelling tps, the stop command does though. I'll just quote Merlini from his Zeus guide here, he talks about Lightning Bolt and even though it might not seem so at first the two spells have a lot in common:

Quote:

Originally Posted by Merlini 1. Lightning Bolt has a very short mini-stun. Some uses are obvious - canceling tps, canceling long channeled spells (Black Hole, Shackle). Others are less obvious. Canceling blink animation of QoP. Interrupting the delicate timing of Earthshaker's Blink Echo, Fissure, Enchant Totem combo. Canceling 1 of your opponent's attacks. The last one may seem ridiculous, who cares about just one attack? My argument is that, in the solo lane, everything matters. One gank, one extra attack thrown in, can upset the balance in one person's favor. Use the mini-stun to maximum effectiveness!

Basically what this means is that sometimes you shouldn't cast Frost Bite right away, instead you wait a second for your opponent to do something and cancel his action. The easiest ones are spells that you can easily predict such as Centaur's Stomp or Panda's Clap but after a while you'll discover more and more. As Merlini said this might not make a huge difference - if you're lucky you're wasting a quarter of a second of your opponent's time. But in the end that split second might just make a difference.

Allies and Enemies

Good allies

AoE disablers

These guys can help you tremendously with landing good ultimates, just remember that neither Overgrowth nor Pit of Malice silence your enemies.

Spammers

I guess this is kind of obvious, Brilliance Aura benefits all heroes that can spam their spells, some more than others.

Juggernaut

The one weakness that Frost Bite has compared to other disables is that it doesn't stop enemies from casting their spells - which really doesn't matter when you are laning with Juggernaut since Blade Fury turns him magic immune anyways. And the 5 second slow from Frost Nova makes it impossible for enemies to escape the Fury.
They form one of the strongest lanes out there and the extra mana from Brilliance Aura allows Juggernaut to farm really quick by using Blade Fury. And what more could a support hero like Crystal Maiden ask for than a well farmed carry on her team?

Omniknight

Omniknight is a great ally for Maiden: They can form a very strong lane, he benefits greatly from her aura and he can repel her for some uninterrupted Freezing Fields.
Too bad he's currently not a very good pick, diffusal blade just counters him too hard.

Tough Enemies

I don't think there's any hard counter to CM. I mean sure, I could list the obligatory Anti Mage and Doom Bringer that come up as counters in every second guide but noone actually uses those to counter Crystal Maiden. Anti Mage is too weak and also Frost Bite disables his blink, Doom is a pain to play against but even if he manages to doom and kill you it's not that bad, I mean usually there are better targets for him than the underfarmed support hero.
Some heroes that are really annoying though are the ones that can dispel Frost Bite and also Bat Rider, because he becomes immune to it once he activates Firefly.

Generally though people do not pick heroes to counter support heroes, so don't worry too much.