Mikaeus, the Unhallowed + Grim Poppet + Goblin Bombardment

Mikaeus, the Unhallowed

Grim Poppet

Goblin Bombardment

How it works

1. Activate Goblin Bombardment by 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. Resolve the Goblin Bombardment ability
4. Repeat.

This loop transforms Mikaeus, the Unhallowed into a relentless recycling engine, granting the undying ability to Grim Poppet so it can return to the battlefield whenever it perishes. Because Grim Poppet enters the battlefield with three -1/-1 counters, you can use its activated ability to strip them away by placing them on other creatures, ensuring it never has a +1/+1 counter on it when it dies and thus permanently resetting its undying trigger. Finally, Goblin Bombardment provides the necessary outlet to sacrifice Grim Poppet repeatedly, turning this endless cycle of death and rebirth into infinite damage dealt to any target.