Prototype Portal, Dross Scorpion, Phyrexian Altar, and Cathodion

Prerequisites

• Prototype Portal on the battlefield
• Dross Scorpion on the battlefield
• Phyrexian Altar on the battlefield
• Cathodion on the battlefield
• available

Steps

1. Activate Prototype Portal by paying and tapping it, creating a token copy of Cathodion
2. Activate Phyrexian Altar by sacrificing Cathodion, adding one mana of any color
3. When Cathodion dies, it and Dross Scorpion trigger
4. Resolve the Cathodion trigger, adding
5. Resolve the Dross Scorpion trigger, untapping Prototype Portal
6. Repeat

Results

• Infinite colored mana
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers