Mikaeus, the Unhallowed, Grim Poppet, and Grimgrin, Corpse-Born

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Grim Poppet on the battlefield
• Grimgrin, Corpse-Born on the battlefield

Steps

1. Activate Grimgrin 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 Grimgrin ability Repeat

Results

• Infinite +1/+1 counters on a creature
• Infinite -1/-1 counters
• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers