Mikaeus, the Unhallowed + Ashnod's Altar + Lesser Masticore

Mikaeus, the Unhallowed

Ashnod's Altar

Lesser Masticore

How it works

1. Activate Ashnod's Altar by sacrificing Lesser Masticore.
2. When Lesser Masticore dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Activate Ashnod's Altar by sacrificing Lesser Masticore.
4. When Lesser Masticore dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
5. Repeat.