Radiant Solar, Sefris of the Hidden Ways, Bloodboil Sorcerer, and Mardu Siegebreaker

Prerequisites

• Radiant Solar on the battlefield
• Sefris of the Hidden Ways on the battlefield
• Bloodboil Sorcerer on the battlefield
• Mardu Siegebreaker in hand
• available

Steps

1. Cast Mardu Siegebreaker by paying its mana cost
2. When Mardu Siegebreaker enters, it and Radiant Solar trigger
3. Resolve the Mardu Siegebreaker trigger, exiling Bloodboil Sorcerer until Mardu Siegebreaker leaves the battlefield
4. Resolve the Radiant Solar trigger, venturing into the Oubliette room, causing you to discard a card and then sacrifice Mardu Siegebreaker
5. Mardu Siegebreaker leaves the battlefield, causing Bloodboil Sorcerer to be returned to the battlefield from exile
6. When Bloodboil Sorcerer enters, it and Radiant Solar trigger
7. Resolve the Bloodboil Sorcerer trigger, venturing into the Cradle of the Death God room, creating a 4/4 legendary The Atropal creature token and completing Tomb of Annihilation
8. If you control two or more The Atropal tokens, put all but one into your graveyard due to the legend rule
9. Sefris' second ability triggers, returning Mardu Siegebreaker from your graveyard to the battlefield
10. When Mardu Siegebreaker enters, it and Radiant Solar trigger
11. Resolve the Mardu Siegebreaker trigger, exiling Bloodboil Sorcerer until Mardu Siegebreaker leaves the battlefield
12. Resolve the Radiant Solar trigger from step 10, venturing into Tomb of Annihilation and into the Trapped Entry room, causing each player to lose 1 life
13. Resolve the Radiant Solar trigger from step 6, venturing into the Oubliette room, causing you to discard a card and then sacrifice Mardu Siegebreaker
14. Repeat from step 5

Results

• Near-infinite ETB
• Near-infinite LTB
• Near-infinite death triggers
• Near-infinite lifeloss for all players
• Near-infinite sacrifice triggers