Svarja, the Iron Valkyrie

Flash, Flying, First Strike
Svarja, the Iron Valkyrie enters the battlefield with X +1/+1 counters on it.
Whenever a creature you control dies you may either put a +1/+1 counter on Svarja, the Iron Valkyrie or remove two +1/+1 counters and put that card into your hand instead of the graveyard.
"Your time is not today."