Nim Deathmantle, and Ashnod's Altar

Prerequisites

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

Steps

1. Activate Ashnod's Altar by sacrificing the persist or undying creature, adding
2. When the persist or undying creature dies, its persist or undying ability and Nim Deathmantle trigger
3. Resolve the Nim Deathmantle trigger, choosing not to pay
4. Resolve the creature's trigger, returning it from your graveyard to the battlefield with a +1/+1 or -1/-1 counter on it
5. Activate Ashnod's Altar by sacrificing the persist or undying creature, adding
6. When the persist or undying creature dies, Nim Deathmantle triggers, causing you to pay to return the persist or undying creature from your graveyard to the battlefield
7. Repeat

Results

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