Nim Deathmantle, Ashnod's Altar, and Urza, Lord High Artificer

Prerequisites

• Nim Deathmantle on the battlefield
• Ashnod's Altar on the battlefield
• Urza, Lord High Artificer on the battlefield
• available

Steps

1. Activate Ashnod's Altar by sacrificing Urza, adding
2. When Urza dies, Nim Deathmantle triggers, causing you to pay to return Urza from your graveyard to the battlefield and attach Nim Deathmantle to it
3. When Urza enters, it triggers, creating a creature token
4. Activate Ashnod's Altar by sacrificing a creature token, adding
5. Repeat

Results

• Infinite blue mana
• Infinite colorless mana
• Infinite creature tokens
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers
• Exile your library
• Infinite creature tokens that are infinitely large
• Cast all spells in your library