Mikaeus, the Unhallowed, Otherworldly Escort, and Yahenni, Undying Partisan

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Otherworldly Escort on the battlefield
• Yahenni, Undying Partisan on the battlefield

Steps

1. Activate Yahenni by sacrificing Otherworldly Escort
2. When Otherworldly Escort dies, it triggers, returning itself from your graveyard to the battlefield as a Spirit Detective
3. Resolve the Yahenni ability
4. Activate Yahenni by sacrificing Otherworldly Escort
5. When Otherworldly Escort dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
6. Resolve the Yahenni ability
7. Repeat

Results

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