Mikaeus, the Unhallowed + Carrion Feeder + Gravelgill Axeshark

Mikaeus, the Unhallowed

Carrion Feeder

Gravelgill Axeshark

How it works

1. Activate Carrion Feeder by sacrificing Gravelgill Axeshark.
2. When Gravelgill Axeshark dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Resolve the Carrion Feeder ability.
4. Activate Carrion Feeder by sacrificing Gravelgill Axeshark.
5. When Gravelgill Axeshark dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
6. Resolve the Carrion Feeder ability.
7. Repeat.

This ingenious loop relies on a brilliant counter-cancellation quirk between two different revival mechanics, using Carrion Feeder as the ultimate sacrifice outlet to keep the cycle spinning. Gravelgill Axeshark enters the fray with a persist trigger that brings it back with a -1/-1 counter, but Mikaeus, the Unhallowed grants it undying, allowing it to return with a +1/+1 counter on the very next death. Because state-based actions cause a +1/+1 counter and a -1/+1 counter to annihilate each other whenever they reside on the same permanent, Gravelgill Axeshark is perpetually cleared of counters and ready to die all over again.