Mikaeus, the Unhallowed, Ashnod's Altar, and Plague Belcher

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Ashnod's Altar on the battlefield
• Plague Belcher on the battlefield

Steps

1. Activate Ashnod's Altar by sacrificing Plague Belcher
2. When Plague Belcher dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
3. When Plague Belcher enters the battlefield, it triggers, putting a -1/-1 counter on it
4. Repeat

Results

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