Mikaeus, the Unhallowed + Canker Abomination + Spawning Pit

Mikaeus, the Unhallowed

Canker Abomination

Spawning Pit

How it works

1. Activate Spawning Pit by sacrificing Canker Abomination.
2. When Canker Abomination dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
3. When Canker Abomination enters the battlefield, it triggers, putting a number of -1/-1 counters on it equal to the number of creatures an opponent controls.
4. If the opponent had seven or more creatures, Canker Abomination will die as a state-based action due to having 0 or less toughness. If this occurs, repeat steps 2 through 4 infinitely.
5. Otherwise, resolve the Spawning Pit ability, and repeat from step 1.
6. Cast Canker Abomination by paying 2B/GB/G.
7. When Canker Abomination enters the battlefield, it triggers, putting a number of -1/-1 counters on it equal to the number of creatures an opponent controls.
8. Canker Abomination dies as a state-based action due to having 0 or less toughness, triggering its undying ability, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
9. Repeat from step 2.