Mikaeus, the Unhallowed + Blasting Station + Grim Poppet

Mikaeus, the Unhallowed

Blasting Station

Grim Poppet

How it works

1. Activate Blasting Station by tapping it and sacrificing Grim Poppet.
2. When Grim Poppet 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 Grim Poppet enters, Blasting Station triggers, untapping Blasting Station.
4. Resolve the Blasting Station ability from step 1
5. Repeat.

This lethal loop relies on Mikaeus, the Unhallowed granting undying to Grim Poppet, ensuring that every time the puppet is sacrificed, it returns to the battlefield with a +1/+1 counter. Because Grim Poppet enters the battlefield with three -1/-1 counters, state-based actions immediately cause those -1/-1 counters and the +1/+1 counter to annihilate each other, resetting the puppet so its undying ability can trigger again on the next iteration. Meanwhile, Blasting Station acts as the engine of the entire operation, dealing damage to any target while its untap trigger resets itself each time Grim Poppet enters the battlefield anew.