Zalvia, Enlightened Outcast

Double Strike
You may exert Zalvia, Enlightened Outcast as it attacks, if you do each opponent loses X life, where X is the number of +1/+1 counters on this permanent. You gain life equal to the life lost this way.
{w}, Pay 4 life: Put a +1/+1 counter on Zalvia and it gains vigilance until end of turn.