Galactus, the Devourer

Annihilator 6 (Whenever this creature attacks,
defending player sacrifices 6 permanents.)
Galactus, the Devourer's toughness is equal
to the number of lands in all graveyards.
Whenever a land an opponent controls is put
into their graveyard from play, you gain 2 life.
"The loss of life when I feed is regrettable... But unavoidable."