Geralf's Messenger, Ashnod's Altar, and Nim Deathmantle

Prerequisites

• Geralf's Messenger on the battlefield
• Ashnod's Altar on the battlefield
• Nim Deathmantle on the battlefield

Steps

1. Activate Ashnod's Altar by sacrificing Geralf's Messenger, adding
2. Nim Deathmantle and Geralf's Messenger's undying ability triggers
3. Resolve the Nim Deathmantle trigger, choosing not to pay for the trigger
4. Resolve the Geralf's Messenger trigger, returning it from your graveyard to the battlefield with a +1/+1 counter on it
5. Geralf's Messenger enters the battlefield, causing target opponent to lose 2 life
6. Activate Ashnod's Altar by sacrificing Geralf's Messenger, adding
7. Nim Deathmantle triggers, causing you to pay to return Geralf's Messenger from your graveyard to the battlefield, and attach Nim Deathmantle to it
8. Geralf's Messenger enters the battlefield, causing target opponent to lose 2 life
9. Repeat

Results

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