Gengar

Flying, undying, menace
Hex {t} Remove a +1/+1 counter from every
creature on the battlefield then, you may play
creature cards from your graveyard this turn if
there are 5 or more cards in exile.
Dream Eater {u/b}{u/b}{b/r}{t} Target opponent exiles
cards from their hand equal to the number of
tapped creatures they control. You may spend
any mana color to cast cards exiled by Gengar.