Expiration Trigger
An Expiration Trigger is defined as a spell that casts another spell after the projectile has run out of lifetime or is destroyed by a spell like Spells To Power.
Expiration Triggers will ignore the usual cast delay modifiers of the spells they contain.
If a projectile with an Expiration Trigger is removed while stationary, including when it dies due to collision with terrain, its payload will be released in a random direction (unconstrained by nearby terrain); this is not the case if it is removed while moving due to hitting an entity, its projectile lifetime or any alternative component lifetime running out, death from the projectile running out of HP (Pollen), or removal via Explosive Detonator, Spells to Power, or other Spells to ... spells.
For more information, see Triggers