Mikaeus, the Unhallowed, Murderous Redcap, and Ashnod's Altar

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Murderous Redcap on the battlefield
• Ashnod's Altar on the battlefield

Steps

1. Activate Ashnod's Altar by sacrificing Murderous Redcap, adding
2. Murderous Redcap's persist and undying abilities trigger
3. Resolve Murderous Redcap's persist ability, returning it from your graveyard to the battlefield with a -1/-1 counter on it
4. Murderous Redcap's undying ability fails to resolve due to having no legal target
5. Murderous Redcap enters the battlefield, dealing damage equal to its power to any target
6. Activate Ashnod's Altar by sacrificing Murderous Redcap, adding
7. Murderous Redcap's undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
8. Murderous Redcap enters the battlefield, dealing damage equal to its power to any target
9. Activate Ashnod's Altar by sacrificing Murderous Redcap, adding
10. Murderous Redcap's persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
11. Repeat from step 5

Results

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