Nim Deathmantle, Ashnod's Altar, and Harried Spearguard

Prerequisites

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

Steps

1. Activate Ashnod's Altar by sacrificing Harried Spearguard, adding
2. When Harried Spearguard dies, it and Nim Deathmantle triggers
3. Resolve the Harried Spearguard trigger, creating a 1/1 Rat creature token
4. Activate Ashnod's Altar by sacrificing the Rat, adding
5. Resolve the Nim Deathmantle trigger from step 2, causing you to pay to return Harried Spearguard 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