Eudza, the Hivemind

Flying
Whenever a permanent an opponent controls is
returned to its owner's hand, you may reveal the
top card of your library. If its converted mana cost
is less than the permanent's, you may cast it
without paying its mana cost.
Sacrifice a Mountain: Return target permanent
an opponent controls to its owner's hand unless
that player has Eudza, the Hivemind deal 4
damage to them.