Nim Deathmantle, Ashnod's Altar, and Doomed Traveler

Prerequisites

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

Steps

1. Activate Ashnod's Altar by sacrificing Doomed Traveler, adding
2. When Doomed Traveler dies, it and Nim Deathmantle triggers
3. Resolve the Doomed Traveler trigger, creating a 1/1 Spirit creature token
4. Activate Ashnod's Altar by sacrificing the Spirit, adding
5. Resolve the Nim Deathmantle trigger from step 2, causing you to pay to return Doomed Traveler from your graveyard to the battlefield, and attach Nim Deathmantle to it
6. Repeat

Results

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