Yelena, Merciless Soul

Ward {x}, where X is the number of experience counters you have.
At the beginning of your end step, if a
permanent you controlled left the battlefield
this turn, you get an experience counter.

Creatures you control get +1/+0 for each experience counter you have.

"To me, it wasn't a devil, but a god, he gave us hope
when we were at our weakest."