Yvanna, the Ivory Thorn

Whenever your life total changes put a +1/+1 counter on Yvanna, the Ivory Thorn.
{2}{w}{t}, Remove X +1/+1 counters from
Yvanna: Gain X life.
{2}{b}{t}, Remove X +1/+1 counters from
Yvanna: Target player loses X life.
She paints masterpieces in ink and blood.