Narmkorat, Vengeant

Flying
Creatures you control are undead. (If their power or toughness would be reduced, it's increased instead and vice versa.)
{4}{b}{b}: All creatures get -2/-2 until end of turn. When this ability finishes resolving, you may return a creature card from a graveyard to the battlefield under your control. Activate only once each turn and only at sorcery speed.