Ghost of the Arena

{t}, pay {w/b}: Tap x target creatures. You gain life equal to the amount of creatures tapped this way. They do not untap during their controller's next untap step.
{t}, pay {x}{x}{w/b}: Destroy {x} target creatures. Each opponent loses life to the total power of creatures destroyed this way. You gain lofe equal to the amount of life lost this way.
Ghost of the Arena's power and toughness are both equal to the amount of life you have gained this game.