Mikaeus, the Unhallowed + Blasting Station + Reaping Willow

Mikaeus, the Unhallowed

Blasting Station

Reaping Willow

How it works

1. Activate Blasting Station by tapping it and sacrificing Reaping Willow.
2. When Reaping Willow dies, its undying ability triggers, returning it from your graveyard to the battlefield without a +1/+1 counter on it due to its replacement effect.
3. When Reaping Willow enters, Blasting Station triggers, untapping Blasting Station.
4. Resolve the Blasting Station ability from step 1
5. Repeat.