Qizay, The Dark One

When Qizay, the Dark One enters the battlefield
you may pay X life. If you do, Qizay enters the battlefield with X +1/+1 counters.
Flying, Lifelink
Whenever you gain life from a nonlegendary
source, put that many +1/+1 counters on Qizay.
{x}, {t}, Remove X +1/+1 counters from Qizay:
Destroy target nonland permanent with converted
mana cost X or less.