Nim Deathmantle, Ashnod's Altar, and Patagia Viper

Prerequisites

• Nim Deathmantle on the battlefield
• Ashnod's Altar on the battlefield
• Patagia Viper on the battlefield
• available

Steps

1. Activate Ashnod's Altar by sacrificing Patagia Viper, adding
2. When Patagia Viper dies, Nim Deathmantle triggers, causing you to pay to return Patagia Viper from your graveyard to the battlefield and attach Nim Deathmantle to it
3. When Patagia Viper enters, it triggers twice
4. Resolve the first trigger, creating two creature tokens
5. Holding priority, activate Ashnod's Altar twice by sacrificing Patagia Viper and a creature token, adding Repeat from step 2

Results

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