Mikaeus, the Unhallowed, Umbral Collar Zealot, and Putrid Goblin

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Umbral Collar Zealot on the battlefield
• Putrid Goblin on the battlefield

Steps

1. Activate Umbral Collar Zealot by sacrificing Putrid Goblin
2. When Putrid Goblin dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. Resolve the Umbral Collar Zealot ability
4. Activate Umbral Collar Zealot by sacrificing Putrid Goblin
5. When Putrid Goblin dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
6. Resolve the Umbral Collar Zealot ability
7. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite death triggers
• Infinite sacrifice triggers
• Infinite surveil