Bel'veth, Empress of the Void

Whenever Bel'veth, Empress of the Void kills
another creature, she adds their current power
and toughness to her own.
You may pay X life to give Bel'veth, Empress
of the Void double strike until end of turn,
where X = Bel'veth's current power.
{b}{r}{t}: Bel'veth, Empress of the Void fights
target creature an opponent controls.