Voracious, Nature's Glutton

Voracious, Nature's Glutton's power and toughness are each equal to the number of cards in all graveyards.
Whenever another creature you control dies, target player puts a number of cards equal to that creature’s power from the top of their library into their graveyard.
{b/g}{b/g} sacrifice a creature: regenerate Voracious, Nature's Glutton