Ancalagon, Advent of Demise

As an additional cost to cast this spell, sacrifice
three Mountains and pay any amount of life.
This spell costs {x} less to cast, where X is the
amount of life you paid this way.
Flying, menace, recurring (You may play this card
from your graveyard if it left the battlefield this turn.)
As long as you control a legendary Dragon, you
can't lose the game and your opponents can't win
the game.