There is a planes chase card that gives instant and sorcery cards "Rebound". I was wondering if I had an instant with "Overload", could I rebound it for it's "Overload" cost?
I believe so because its an alternate cost, and it's not an x=0 thing, or a kicker thing.
No, alternate costs like overload are separate. When a spell rebounds, you are casting it for free, which disallows you from paying alternate costs.
{Cast Through Time}, {Mizzium Mortars}
RESOLVED