Shryla, Abysmal Wanderer

Whenever a player sacrifices one or more
creatures, you may gaze into the Abyss. Do this
only once each turn.
{t}, Exile a card from your hand: Choose target
creature card in your graveyard. If that card's
mana value is equal to your Abyss' activated
ability number, return it to the battlefield under
your control at the beginning of the next end
step.