Undercity Stalker

Evolve (Whenever a creature enters the battlefield under your control, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Whenever Undercity Stalker evolves, put a +1/+1 counter on it and you lose 2 life.
When a Golgari sewer carrying discarded Simic genes was struck by lightning from an Izzet experiment, it was born.