XZ-Tank Cannon

First strike, trample, haste
{1}{r}, discard a card: XZ-Tank Cannon deals 4
damage to target player. Activate only once per
turn and only as a sorcery.
If XZ-Tank Cannon would die, exile it instead.
Then return to the battlefield one of the original creatures used to meld it.
(Melds with Y-Dragon Head.)