Prototype Portal, Dross Scorpion, Cathodion, and Yahenni, Undying Partisan

Prerequisites

• Prototype Portal on the battlefield
• Dross Scorpion on the battlefield
• Cathodion on the battlefield
• Yahenni, Undying Partisan on the battlefield
• available

Steps

1. Activate Prototype Portal by paying and tapping it, creating a token copy of Cathodion
2. Activate Yahenni by sacrificing Cathodion
3. When Cathodion dies, Cathodion and Dross Scorpion trigger
4. Resolve the Cathodion trigger, adding
5. Resolve the Dross Scorpion trigger, untapping Prototype Portal
6. Resolve the Yahenni ability, giving it indestructible until end of turn
7. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers