Nim Deathmantle, Ashnod's Altar, and Imperious Oligarch

Prerequisites

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

Steps

1. Activate Ashnod's Altar by sacrificing Imperious Oligarch, adding
2. When Imperious Oligarch dies, it and Nim Deathmantle trigger, Resolve the Imperious Oligarch trigger, creating a creature token
3. Holding priority, activate Ashnod's Altar by sacrificing a creature token, adding
4. Resolve the Nim Deathmantle trigger, causing you to pay to return Imperious Oligarch from your graveyard to the battlefield and attach Nim Deathmantle to it
5. Repeat

Results

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