Skellek, Varakna Ritualist

Whenever a creature enters the battlefield from
an opponent's graveyard, Skellek deals damage to
that opponent equal to that card's converted
mana cost.
{b/g}{b/g}, {t}, Sacrifice a creature: Put target
creature card with converted mana cost equal to
1 plus the sacrificed creature's converted mana
cost from a graveyard onto the battlefield under
your control. You lose life equal to its converted
mana cost.