Ability Stages:
When designing an ability, the designer has the option to assign times for the stages Prepare, Channel and Finish. When setting all these values to zero, the ability will be instantly cast.
Prepare
The Prepare stage is mostly for abilities with a high gameplay value. It gives the designer the possibility to add additional time which the caster has to "sacrifice" in order to cast the Ability. Also, ability casts can be interrupted by enemies in this stage.
Cast
The Cast stage has no duration and is a point in time. At this point, the unit must pay the cast cost.