Mikaeus, the Unhallowed + Putrid Goblin + Yahenni, Undying Partisan

Mikaeus, the Unhallowed

Putrid Goblin

Yahenni, Undying Partisan

How it works

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