Mikaeus, the Unhallowed + Carrion Feeder + Grazing Kelpie

Mikaeus, the Unhallowed

Carrion Feeder

Grazing Kelpie

How it works

1. Activate Carrion Feeder by sacrificing Grazing Kelpie.
2. When Grazing Kelpie 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 Grazing Kelpie.
5. When Grazing Kelpie 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.