Xaxorox the Ravenous

Flying,Partner with Azella, Zealous Sanguimancer
At the beginning of your end step, each opponent
loses life equal to the number of +1/+1 counters
on Xaxorox the Ravenous, and you gain life equal
to the life lost this way.
{1}{b}, pay 2 life, sacrifice a creature: Put a +1/+1 counter on Xaxorox. Activate this ability only
any time you would cast a sorcery.