Brotherhood Outcast, Unhallowed Pact, and Yahenni, Undying Partisan

Prerequisites

• Brotherhood Outcast on the battlefield
• Unhallowed Pact on the battlefield
• Yahenni, Undying Partisan on the battlefield

Steps

1. Activate Yahenni by sacrificing Brotherhood Outcast
2. When Brotherhood Outcast dies, Unhallowed Pact triggers, returning Brotherhood Outcast from your graveyard to the battlefield
3. When Brotherhood Outcast enters the battlefield, it triggers, returning Unhallowed Pact from your graveyard to the battlefield attached to Brotherhood Outcast
4. Resolve the Yahenni ability
5. Repeat

Results

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