Mikaeus, the Unhallowed + Shilgengar, Sire of Famine + Heartmender

Mikaeus, the Unhallowed

Shilgengar, Sire of Famine

Heartmender

How it works

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