Scion of the Evening Star

Flying
Scion of the Evening Star enters the battlefield with X +1/+1 counter on it.
{b}{b}, Remove a +1/+1 counter from Scion
of the Evening Star: Target opponent loses
1 life and you gain 1 life. You may have that
opponent can't gain life until end of turn.
If you don't, they discard a card.