Crystal Maiden

Rylai the Crystal Maiden is a ranged intelligence Hero used as a hard support and disabler. She is perhaps best known for her powerful global mana regeneration aura. This aura allows mana dependent allies to excel during the early to mid game and the laning phase, and allows her to constantly activate her own spells without needing to worry much about the mana costs. She also has a high amount of early game presence with just a few points in her Crystal Nova and Frostbite abilities. Crystal Nova is a powerful area-of-effect nuke that slows both attack and movement speeds of enemies within an area for several seconds, while Frostbite encases an enemy in a block of ice for several seconds, immobilizing it and doing moderate damage per second. Combining these two abilities together along with a laning partner's own spells often results in the quick death of an enemy hero. Although her strong early game presence is quickly lost due to her extreme frailty and poor mobility, she can still inflict a heavy amount of damage in teamfights later on if she is able to channel her deadly ultimate, Freezing Field. Her Arcane Aura, strong disabling and nuking prowess, relative ease of usage, and almost complete lack of item dependence makes her a reliable support caster that can be useful in any team.

Tips

 * Crystal Maiden's potent disables grant her a powerful early-game roaming and ganking presence, particularly when her slow base movement speed is offset by Tranquil Boots.
 * Because of her low base movement speed, Rylai benefits greatly from positioning items such as Blink Dagger and Force Staff. When not spending gold on support or survivability items, it is wise to invest in positioning items.
 * is a large area of effect nuke that also slows your enemies. You can hit enemies from 1100 units away with it (700 casting range + 400 radius), applying the slow and allowing you and your teammates to catch up to fleeing foes to disable them further.
 * In teamfights, cast Crystal Nova early on, as the movement speed slow can hinder enemies' movements and set up spells for teammates while the attack speed slow can reduce their ability to fight.
 * Crystal Nova can be used to help push a lane without contesting carries for last hits, as the damage is not quite enough to kill a wave of creeps. However, make sure to keep it off cooldown in the possibility of an upcoming teamfight.
 * is a great rooting disable which prevents the target from moving or attacking. It also interrupts channelling spells and teleports by applying a mini-stun upon cast. Unfortunately, it does not prevent enemy heroes from casting spells (except for True blinks).
 * Frostbite has an instant cast time. As such, if you need to instantly disable an enemy regardless of cast animation, Frostbite is a good option.
 * Frostbite lasts 10 seconds on creeps, no matter what level it is. This can be useful for jungling on the side as it will deal 1000 damage to neutrals, and can be useful for rooting enemy-controlled creeps during fights.
 * Frostbite's up-time increases drastically as it is leveled, as the cooldown decreases in tandem with the disable duration's increase. At level 4, it is possible to keep an enemy rooted for almost 43% of the time.
 * benefits the whole team greatly, especially one with a strong caster/ganker line-up, as it grants them a better lane presence due to the increased number of spells they can use. Even past the laning stage, at max level it equates to using on all teammates globally whenever it is off cooldown, which allows all allied heroes, especially those with small mana pools, to cast spells much more frequently.
 * It is wise to get at least one level of Arcane Aura in the early game. As Rylai's low base Intelligence greatly limits her ability to cast her disables during the laning stage, having some form of early mana replenishment goes a long way towards giving you more casting power.
 * When choosing when to level up Arcane Aura, you should bear in mind your team's composition, as well as that of the enemy. If the enemy has numerous mana-destroying spells or your team can benefit from the mana regen in-lane, then taking at least a couple early levels can give your team the freedom to use their spells more frequently. However, bear in mind that this comes at the cost of your ability to disable the enemy in the early game.
 * is an incredibly strong spell. However, it can be unpredictable and usually gets interrupted by your enemies almost immediately if cast at the wrong time. Freezing Field also consumes a lot of mana at higher levels, so use it sparingly.
 * When positioning yourself to cast your ultimate, try to utilize trees and high ground as cover if the option presents itself. By shielding yourself in the fog of war, the enemy loses the ability to use targeted stuns to interrupt you, increasing the odds of channeling the spell for a longer duration.
 * Prior to casting Freezing Field, it is recommended that you cast Crystal Nova on as many enemies as possible first, as the slows stack. Slowing the enemy's movement speed by 60% and their attack speed by 60 can go a long way towards locking them down for your team to capitalize on.
 * In general, it is not recommended to level up Freezing Field immediately when it is available, as it is highly situational and increases drastically in mana cost as it's skilled more. However, its slow and gigantic (if unpredictable) damage can be very useful in early game, especially against enemies that lack the means to interrupt it, so taking one point in it early on and leaving it at level 1 until much later can give you access to the ultimate while preserving your mana pool and freeing up your skill points for other abilities. Overall, let your decision be informed by enemy line-up as well as laning composition.
 * Freezing Field must be used at the right time to avoid interruption and being focused. Generally speaking, in an encounter it is best used after the initial nuking phase, when the enemy's stuns are on cooldown. If your team has an initiator with the capability to disable a group of enemies, such as 's or 's, Freezing Field should be used in tandem with their mass disable. Using Freezing Field very often results in Rylai's death if cast out in the open, and she rarely is able to channel it for its full duration, but if she can maintain it even for a few seconds it will be useful for her team.
 * When ganking, it is important to layer your disables, even among your own spells. While Crystal Nova's 15 second cooldown ensures that it can only be used once in a gank, Frostbite's 7 second cooldown at max level allows you to cast it twice in quick succession. Therefore, the most effective way to disable a target is to Frostbite them first, and then apply Crystal Nova right before its duration ends. This will slow the enemy immediately when Frostbite ends, and the slow will last for up to 5 seconds, enough time for Frostbite to come off of cooldown and be cast a second time, enabling you to keep an enemy in place for up to 10 seconds.
 * Played as a hard support, Crystal Maiden benefits from the utility of many items:
 * Besides Observer Wards, s should also be frequently purchased in order to de-ward enemy wards. As well, upgrading the courier to a greatly benefits the team.
 * is useful to build on roaming Crystal Maidens as an alternative to Bracer, as it can add to her damage nukes or be used to recover health after ganks. The additional Strength gives her more HP, while the mana regeneration works alongside Arcane Aura to keep her mana topped up.
 * is a good cheap support item to build on Crystal Maiden if saving up for a Blink Dagger is unfeasible. It provides Rylai with repositioning abilities, and increases the size of her mana pool.
 * is a decent utility item that gives Rylai many benefits. Besides the all-around stats, the additional armor helps her survive against physical damage, and the magic resistance reduction against enemies allows her to do more damage with her magic nukes, especially Freezing Field.
 * serves as both a utility and survivability item. The Strength and evasion give Crystal Maiden more HP and survivability against physical attacks, while the active disarm can be used to halt an enemy carry from attacking in teamfight situations.
 * In a pinch, can serve as a poor man's substitute for Black King Bar. Used on yourself right before casting your ultimate, it can shield you with an umbrella of invisibility that prevents the enemy from hitting you with targeted disables as long as they don't have detection. However, it is not a wise pickup if one of your allies already has invisibility-based abilities, as the enemy will more likely have detection on hand to counter them.

Trivia

 * Rylai's name in Warcraft DotA was Rylai Crestfall. Her surname was removed in transition to Dota 2 for the implementation of her sibling rivalry with Lina.
 * Crystal Maiden's used to be named Brilliance Aura.
 * In early versions of DotA, Crystal Maiden and used to share the same  ability (although they were both named Frost Nova). However, in later updates, Crystal Maiden's Frost Nova was changed to Crystal Nova, turning it into a free-cast area-of-effect ability, while Lich kept the original effects.
 * League of Legends features an item called Rylai's Crystal Scepter, a homage to the Crystal Maiden from the original DotA.
 * In World of Warcraft an alliance NPC is named Rylai Crestfall, a homage to the original Crystal Maiden from Warcraft III's DotA.
 * Crystal Maiden's leveling-up response cm levelup 03.mp3 "Is it cold in here or is it just me?" is a reference to the action movie Demolition Man.
 * Crystal Maiden's respawning line cm respawn 03.mp3 "You only live ice..." is a reference to the 1967 James Bond film You Only Live Twice based on the novel of the same name.
 * Crystal Maiden's line cm battlebegins 01.mp3 "It's all fun and games until someone's frozen solid." is a reference to a novel written by Christopher Brookmyre entitled All Fun and Games until Somebody Loses an Eye.
 * Crystal Maiden's rare response cm rare 02.mp3 "Can you guess my... favorite poet?" is a reference to Robert Frost due to his last name.