Ghyrson Starn, Kelermorph, Gisela, Blade of Goldnight, Double Major, and Switcheroo

Prerequisites

• Ghyrson Starn, Kelermorph in hand
• Gisela, Blade of Goldnight on the battlefield
• Double Major in hand
• Switcheroo in hand
• An opponent controls a creature
• You have a way to deal exactly two or three damage to an opponent
• You have enough mana to cast Switcheroo
• available

Steps

1. Cast Switcheroo by paying its mana cost, giving control of Gisela to an opponent
2. Cast Ghyrson Starn by paying
3. Holding priority, cast Double Major by paying , creating a copy of the Ghyrson Starn spell that isn't legendary
4. Resolve both Ghyrson Starn spells
5. Deal exactly two or three damage to the opponent, which is reduced to one by Gisela, triggering Ghyrson Starn and the Ghyrson Starn token
6. Resolve the nontoken Ghyrson Starn's trigger, dealing 1 damage to the opponent
7. The token Ghyrson Starn triggers, dealing 1 damage to the opponent
8. The nontoken Ghyrson Starn triggers, dealing 1 damage to the opponent
9. Repeat from step 7

Results

• Infinite damage to target opponent