Crystal Maiden

Rylai the Crystal Maiden is a ranged intelligence Hero who uses the power of frost and ice to disable her foes.

Renowned as a well-balanced hard support, Crystal Maiden possesses strong nukes and disables that allow her to apply strong slows to enemies. 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 them and dealing moderate damage per second. Combining these two abilities together along with a laning partner's own spells is often enough to bring an enemy hero to their knees. Her Arcane Aura passive will also regenerate mana for Rylai and her allies, greatly boosting their ability to cast spells in the early game. Although her strong early game presence can be countered by 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 global mana aura, strong disabling and nuking prowess, simple spell layout, and almost complete lack of item dependence makes Crystal Maiden a reliable support caster that can be a strong asset to any team, and judicious use of her ultimate allows her to lay waste to her enemies when used properly. With protection from her team and appropriate item selection, she can be the only support any team needs.

Recommended items
Starting items:
 * One each of and  provides Crystal Maiden with enough basic regen to remain in-lane and support her teammates without being harassed away and being forced to return to base.
 * is a useful purchase due to Crystal Maiden's low base intelligence preventing her from casting too many spells in the laning stage. The additional mana replenishment can allow her to bring both of her disables to bear on an enemy, greatly increasing the odds of a kill during a gank.
 * can give Crystal Maiden more HP, which can help extend her survivability.
 * Buying the at game start is expected of support heroes due to their item independence.
 * s should be purchased regularly and placed at key areas around the map. As a support, giving your team map vision is critical to victory.

Early game:
 * is useful for giving Crystal Maiden burst regen, particularly due to her small HP and mana pools. In a pinch, the burst mana regen of a full-charge Magic Stick can allow her to cast or  in an emergency.
 * are a crucial early purchase on Crystal Maiden due to her extremely low base movement speed. Increasing her mobility allows Rylai to get within range to cast her disables on her foes, or outrun pursuing enemies.
 * can be upgraded from Gauntlets of Strength to provide a good mix of attributes, the strength bonus being especially useful to improve Crystal Maiden's survivability.
 * is mandatory for all heroes, but should be carried in surplus on Crystal Maiden as her disables can drastically turn ganks around.
 * is important to purchase as early as possible if gold permits, in order to facilitate delivery of items to teammates around the map.

Core items:
 * is very useful on Crystal Maiden as it is a cheap way to give her stats and more survivability, key requirements for hard support heroes. The increased charge storage also allows her to restore up to 255 HP and mana instantly, which can allow her to do more in fights.
 * are the cheapest upgradable boots available, and allow Crystal Maiden to remain out in the field for extended periods of time. As restores her mana pool while Tranquil Boots's passive heals her, Crystal Maiden can stay out in the field indefinitely and never need to return to base. The increased movement speed and extra armor are also a boon, allowing her to roam, gank and flee more effectively.
 * 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 to allow her to cast her disables more easily.
 * augments Rylai's mobility, allowing her to instantly jump within range for locking down enemy heroes with her disables. The improved mobility also allows her to move around the map more easily to support her teammates, or escape pursuing enemies.
 * gives Crystal Maiden stats across the board and can be upgraded from an already-purchased Bracer. The extra movement speed can also increase her movement speed, allowing her to position herself for casting spells more easily.
 * s should be regularly purchased in order to destroy enemy Observer Wards, as well as to counter invisible enemy heroes.

Situational items:
 * is an expensive luxury item that should be considered only if given farm priority and all other support duties have been met. It prevents interruptions to her ultimate, as well as increasing the size of Rylai's health pool.
 * can give Crystal Maiden a large amount of lockdown ability with, as well as give her stats across the board, particularly her health and mana pool, giving her both extra survivability to cast the ultimate and the mana to do so at higher levels. If your team can prevent Freezing Field from being interrupted, it can be a strong luxury item to invest in once you have the mobility to deploy it reliably.
 * grants Crystal Maiden additional movement speed, allowing her to be more mobile, and grants her a larger mana pool and mana regeneration. The active can be cast on yourself to make yourself temporarily invulnerable while also removing debuffs, or as an additional disable against enemies.
 * gives survivability against auto-attacking carries by granting Rylai a brief period of invulnerability to physical damage, as well as some additional stats. The active is also useful for shielding her from attack damage during Freezing Field, preventing enemies from ending the channel by attacking her.
 * is a very expensive support item, however it gives a very reliable ranged hard-disable, a larger mana pool and some more HP, and a powerful mana regeneration boost.
 * gives Crystal Maiden a strong area slow which synergizes with Crystal Nova and Freezing Field. The armor bonus also makes her much more resistant to physical damage, making it harder to focus her down.
 * can be a useful item to purchase if you intend on making use of Freezing Field regularly, and is otherwise a good support item. Casting the active on yourself prior to jumping in with your ultimate can give you a little extra time to channel it, allowing you to deal more damage. In other situations, it can give you or an ally the ability to stealthily initiate on targets you have vision on, or can be used as an escape or survivability tool by granting someone on your team invisibility and greatly increased magic resistance.
 * is a useful alternative to Bracer when purchased as a stat booster. It provides a useful amount of bonus intelligence, bolstering Rylai's meager base mana pool and allowing her to cast her spells more readily as needed. It can build into a Veil of Discord later in order to provide utility to her team.
 * is a good utility item to build over Bracer as a roaming Crystal Maiden, as it can add to her damage nukes or be used to recover health after ganks. The additional strength gives her HP, while the mana regeneration works alongside Arcane Aura to keep her mana topped up.
 * is a cheap utility item that gives Rylai many benefits. Besides the all-around stats, the additional armor helps her survive against physical damage, the greatly increased intelligence improves the size of her mana pool, and the magic resistance reduction against enemies allows her to do more damage with her magic nukes, especially Freezing Field.
 * is a strong caster item that greatly improves Crystal Maiden's disabling capabilities. The item provides additional mana, improving the utility of Arcane Aura and facilitating casting spells from her small mana pool, and the HP regen works alongside Tranquil Boots in keeping her health topped up. The increased cast range allows Rylai to cast Frostbite and Crystal Nova from longer ranges to catch enemies with her disables, while the spell damage amp increases the lethality of her nukes.
 * is a situational purchase that can improve Crystal Maiden's ability to support her team. It improves her overall stats while providing extra armor, and the active allows her to heal her teammates and herself in teamfights, improving overall team survivability.

Trivia

 * Rylai is one of the oldest heroes from the original DotA in Reign of Chaos DotA. Her title used to be Frost Maiden.
 * 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.
 * In Warcraft DotA, Crystal Maiden's can freeze the enemy's Fountain and the duration was counted as creep.
 * 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.