Mikaeus, the Unhallowed, Ashcloud Phoenix, and Yahenni, Undying Partisan

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Ashcloud Phoenix on the battlefield
• Yahenni, Undying Partisan on the battlefield

Steps

1. Activate Yahenni by sacrificing Ashcloud Phoenix
2. When Ashcloud Phoenix dies, it triggers, as well as its undying ability if it does not have a +1/+1 counter on it
3. Resolve the first trigger, returning it from your graveyard to the battlefield face-down
4. Resolve the second trigger, doing nothing
5. Activate Yahenni by sacrificing Ashcloud Phoenix
6. When Ashcloud Phoenix dies, it triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
7. Resolve the Yahenni abilities from steps 1 and 5
8. Repeat

Results

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