Nether Star

When this artifact enters the battlefield from outside the game, you may pay {x}. If you do, put X charge counters on it.
{t}, Remove any number of counters from among permanents you control: Add X mana in any combination of colors. You gain X life.
{w}{w}, {t}, Sacrifice this artifact: You gain 2 life for each creature target player controls. Activate only at sorcery speed.