Thanos' Sacrifice

Gain control of target creature an opponent
controls until end of turn. Untap that creature.
It gains haste until end of turn. You may sacrifice
a creature you control. If you do, search your
library and/or graveyard for a card named Soul
Stone, reveal it, and put it into your hand. If you search your library this way, shuffle it.
"I ignored my destiny once, I can not do that again.
Even for you. I'm sorry, Little One." —Thanos