Channeling

Channeling an ability causes the caster to stop acting for the duration of the spell. Channeled spells may be ended when the channeling unit takes another action or is interrupted by another spell. While spells are being channeled, a draining bar will appear on the screen, indicating how much time is left in the channel.

Interrupting Channeled Abilities
If the channeling unit is issued another command, such as to move, stop, or attack, the unit will disrupt their channeling. Casting other spells or using items will also interrupt channeling, with the exception of toggled abilities, Wind Walk abilities, a few other abilities like whirling death, and items such as Shiva's Guard, and Phase Boots.

Any disable that would normally prevent a unit from casting the spell in question will also interrupt channeling. This includes Stuns, Mini-Stuns, Pauses, Cyclones, Hexes, and Sleeps. Though they do not prevent casting, Entangle and Ensnare effects will also interrupt channeling. Silence will interrupt channeling from abilities only, while Doom and Static Storm (with Aghanim's Scepter) will interrupt channeling from items as well. Some spells that forcibly move units, such as Dark Seer's Vacuum or Kunkka's X Marks the Spot, will interrupt channeling as well, even if used on friendly units, however, other spells like Force Staff and, will not interrupt channeling.

All channeled abilities expend mana and go on cooldown as soon as they are cast. This means if the channel is interrupted before the spell's effects occur, the mana and cooldown will be wasted, and the spell's effect will be cut short, and in some cases will not perform their effects at all. This is in contrast to other, non-channeled spells with high cast times, such as Assassinate and Requiem of Souls, which will not expend mana or go on cooldown until the spell has been completed. Certain channeled spells, such as Illuminate and Powershot, will still perform their effect even if they are cancelled, usually at the cost of damage.