Mortal Strike

If you control Wraith King you may cast this spell without paying its mana cost.
Target creature gets +2/+0 and gains deathtouch
until end of turn.
Rebound (If you cast this spell from your hand, exile
it as it resolves. At the beginning of your next upkeep,
you may cast this card from exile without paying its
mana cost.)
I decree you deceased.