Terror effects are applied after a roll when you cannot complete a task and at least one of the dice shows a terror icon.
Is it possible to avoid the terror effect by 'securing' the terror die on a spell (assuming no other dice show a terror icon), effectively just failing the task and having to discard a die?
Or does the terror effect apply immediately?
EDIT: After reading the following in the errata, I'm leaning more towards my understanding that they are no longer in the pool and hence do not play a part unless I chose to use them.
Spells that hold dice are cast after a player’s roll, not before. The player looks at the roll, then, if he wishes to save a particular die, casts the spell and places the die on the spell. The ‘held’ die remains on the spell card until used to complete a task or until removed (as described below).