Hallowed Spiritkeeper, Nim Deathmantle, and Ashnod's Altar

Prerequisites

• Hallowed Spiritkeeper on the battlefield
• Nim Deathmantle on the battlefield
• Ashnod's Altar on the battlefield
• You have at least two creature cards in your graveyard

Steps

1. Activate Ashnod's Altar by sacrificing Hallowed Spiritkeeper, adding
2. Hallowed Spiritkeeper dies, triggering itself and Nim Deathmantle
3. Resolve the Hallowed Spiritkeeper trigger, creating at least two 1/1 Spirit creature tokens
4. Activate Ashnod's Altar by sacrificing a Spirit token, adding
5. Resolve the Nim Deathmantle trigger from step 2, causing you to pay to return Hallowed Spiritkeeper from your graveyard to the battlefield, and attach Nim Deathmantle to it
6. Repeat

Results

• Infinite colorless mana
• Infinite creature tokens
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers