Azlask, the Swelling Scourge - Modern Horizons 3 Commander

Whenever Azlask, the Swelling Scourge or another colorless creature you control dies, you get an experience counter.

: Creatures you control get +X/+X until end of turn, where X is the number of experience counters you have. Scions and Spawns you control gain indestructible and annihilator 1 until end of turn.