Dota 2/Rylai the Crystal Maiden

Crystal Maiden is a ranged intelligence hero that is almost always played as a dedicated support. She has a very helpful aura that covers the entire map, giving her allies mana regeneration. She is also a great disabler with her Crystal Nova and Frostbite. Her ultimate, Freezing Field, can hinder any hero's escape as her teammates catch up. Crystal Maiden, being a support intelligence hero, is very frail. Get caught out of position, and she will go down within seconds.

Crystal Nova
Crystal Nova lets you cast a damaging burst of ice that slows enemy movement speed and attack speed. A useful slow, it can slow a bunch of enemies at once. The movement speed slow inhibits an enemy hero's escape, while in the late game the attack speed slow helps nullify the enemy carry's high damage output.
 * Ability: Target Point
 * Damage Type: Magical
 * Damage: 100/150/200/250
 * Duration: 3.5/4/4.5/5
 * Radius: 400
 * Movement Slow: 30%
 * Attack Slow: 20%
 * Mana Cost: 100/120/140/160
 * Cooldown: 15

Frostbite
Frostbite encases an enemy unit in ice, preventing them from moving or attacking but still let's them use abilities other than teleportation abilities. It is a very useful spell for holding a mobile hero like Storm Spirit in place, as well as disabling heroes that rely on their normal attacks a lot. Learn which target will be disabled the worse with Frostbite. Disabling a Lina won't be very helpful to your team since she can still use her high damage spells, but disabling Anti-Mage will make him almost useless to his team.
 * Ability: Target Unit
 * Damage Type: Magical
 * Damage: 70
 * Duration: 1.5/2/2.5/3
 * Mana Cost: 115/125/140/150
 * Cooldown: 10

Arcane Aura
Arcane Aura is a passive skill that will grant a boost in mana regeneration for every ally on the map. That's about 25 levels of intelligence. In comparison, the Ring of Bassilius only grants 0.65 bonus mana regeneration. A very helpful ability especially if you have any mana-intensive heroes on your team.
 * Ability: Passive, Aura
 * Mana Regen: 0.5/1/1.5/2