Giant Killer

An adventurer card is a permanent card in every zone except the stack, as well as while on the stack if not cast as an Adventure. Ignore its alternative characteristics in those cases. For example, while it's in your graveyard, Giant Killer is a white creature card whose mana value is 1. It can't be the target of the triggered ability of Mystic Sanctuary.

You must still follow any timing restrictions and permissions for the permanent spell you cast from exile. Normally, you'll be able to cast it only during your main phase while the stack is empty.

If an effect copies an Adventure spell, that copy is exiled as it resolves. It ceases to exist as a state-based action; it's not possible to cast the copy as a permanent.