Thanatos, Lord of Darkness

{t}{b}{b}{x}: Return X cards from your graveyard
to the battlefield under your control.
When Thanatos, Lord of Darkness
enters the battlefield, give one player a
Curse of Thanatos counter. When a player has a
Curse of Thanatos counter on him/her, that
player must sacrifice a creature at the beginning
of every turn.
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"Serve me, and you shall have my gift of immortality.
Anger me, and you shall burn in Tartarus."