Mikaeus, the Unhallowed + Kithkin Spellduster + Yahenni, Undying Partisan

Mikaeus, the Unhallowed

Kithkin Spellduster

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing Kithkin Spellduster.
2. When Kithkin Spellduster 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 Kithkin Spellduster.
5. When Kithkin Spellduster 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.