Mikaeus, the Unhallowed, Umbral Collar Zealot, and Thunderblust

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Umbral Collar Zealot on the battlefield
• Thunderblust on the battlefield

Steps

1. Activate Umbral Collar Zealot by sacrificing Thunderblust
2. When Thunderblust 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 Thunderblust
5. When Thunderblust 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