Brotherhood Outcast, Ashnod's Altar, and Necrogen Communion

Prerequisites

• Brotherhood Outcast on the battlefield
• Ashnod's Altar on the battlefield
• Necrogen Communion on the battlefield

Steps

1. Activate Ashnod's Altar by sacrificing Brotherhood Outcast
2. When Brotherhood Outcast dies, Necrogen Communion triggers, returning Brotherhood Outcast from your graveyard to the battlefield
3. When Brotherhood Outcast enters the battlefield, it triggers, returning Necrogen Communion from your graveyard to the battlefield attached to Brotherhood Outcast
4. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite colorless mana