Mikaeus, the Unhallowed + Blasting Station + Heartmender

Mikaeus, the Unhallowed

Blasting Station

Heartmender

How it works

1. Activate Blasting Station by tapping it and 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. When Heartmender enters, Blasting Station triggers, untapping Blasting Station.
4. Resolve the Blasting Station ability from step 1.
5. Activate Blasting Station by tapping it and sacrificing Heartmender.
6. When Heartmender dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
7. When Heartmender enters, Blasting Station triggers, untapping Blasting Station.
8. Resolve the Blasting Station ability from step 5.
9. Repeat.