Shredder, Shadow Master, and Archfiend of Despair

Prerequisites

• Shredder, Shadow Master on the battlefield
• Archfiend of Despair on the battlefield

Steps

1. Declare Shredder as an attacker
2. Shredder's first ability triggers, creating a tapped and attacking copy of it attacking each other opponent that isn't legendary
3. Deal combat damage using the Shredders
4. Each Shredder triggers, causing each opponent to lose half their life total, rounded up
5. At the beginning of your end step, Archfiend of Despair triggers, causing each opponent to lose life equal to the life they lost this turn
6. Each opponent then loses the game due to having 0 or less life

Results

• Each opponent loses the game
• Infinite lifeloss