Mikaeus, the Unhallowed, Grimgrin, Corpse-Born, and Reluctant Dounguard

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Grimgrin, Corpse-Born on the battlefield
• Reluctant Dounguard on the battlefield

Steps

1. Activate Grimgrin by sacrificing Reluctant Dounguard
2. When Reluctant Dounguard 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 creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers