Aatrox, World Ender

Trample, indestructible
Whenever Aatrox deals combat damage, each player loses that much life.
If Aatrox would leave the battlefield while The Blood Well has 5 or more counters on it, remove all counters from The Blood Well, then exile Aatrox and return him to the battlefield with +1/+1 counters on him equal to the number of counters removed from The Blood Well this way.
"I am not your enemy. I am the enemy."