Cast Hostage Taker by paying its mana cost.
When Hostage Taker enters, it and Radiant Solar trigger.
Resolve the Hostage Taker trigger, exiling Bloodboil Sorcerer until Hostage Taker leaves the battlefield.
Resolve the Radiant Solar trigger, venturing into the Oubliette room, causing you to discard a card and then sacrifice Hostage Taker.
Hostage Taker leaves the battlefield, causing Bloodboil Sorcerer to be returned to the battlefield from exile.
When Bloodboil Sorcerer enters, it and Radiant Solar trigger.
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.
If you control two or more The Atropal tokens, put all but one into your graveyard due to the legend rule.
Sefris' second ability triggers, returning Hostage Taker from your graveyard to the battlefield.
When Hostage Taker enters, it and Radiant Solar trigger.
Resolve the Hostage Taker trigger, exiling Bloodboil Sorcerer until Hostage Taker leaves the battlefield.
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.
Resolve the Radiant Solar trigger from step 6, venturing into the Oubliette room, causing you to discard a card and then sacrifice Hostage Taker.
Repeat from step 5.

Near-infinite creature ETB

Near-infinite creature LTB

Near-infinite death triggers

Near-infinite lifeloss for all players

Near-infinite creature sacrifice triggers

Radiant Solar

Sefris of the Hidden Ways

Hostage Taker

Bloodboil Sorcerer

Cast Faceless Butcher by paying its mana cost.
When Faceless Butcher enters, it and Radiant Solar trigger.
Resolve the Faceless Butcher trigger, exiling Bloodboil Sorcerer.
Resolve the Radiant Solar trigger, venturing into the Oubliette room, causing you to discard a card and then sacrifice Faceless Butcher.
When Faceless Butcher dies, it triggers, returning Bloodboil Sorcerer from exile to the battlefield.
When Bloodboil Sorcerer enters, it and Radiant Solar trigger.
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.
If you control two or more The Atropal tokens, put all but one into your graveyard due to the legend rule.
Sefris' second ability triggers, returning Faceless Butcher from your graveyard to the battlefield.
When Faceless Butcher enters, it and Radiant Solar trigger.
Resolve the Faceless Butcher trigger, exiling Bloodboil Sorcerer.
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.
Resolve the Radiant Solar trigger from step 6, venturing into the Oubliette room, causing you to discard a card and then sacrifice Faceless Butcher.
Repeat from step 5.

Faceless Butcher

Complete a dungeon.
Sefris' second ability triggers twice due to Delney.
Resolve the first trigger, returning up to one other creature from your graveyard to the battlefield.
Resolve the second trigger, returning Bloodboil Sorcerer from your graveyard onto the battlefield.
When Bloodboil Sorcerer enters, it triggers once and Preston triggers twice due to Delney.
Holding priority, activate Thermopod by sacrificing Bloodboil Sorcerer.
Resolve a Preston trigger, creating a token copy of Bloodboil Sorcerer that is a 0/1 Illusion.
When the Bloodboil Sorcerer token enters, it triggers twice due to Delney.
Resolve the Bloodboil Sorcerer token triggers, venturing into Undercity twice.
Resolve the second Preston trigger from step 5, creating a token copy of Bloodboil Sorcerer that is a 0/1 Illusion.
Repeat steps 8 and 9 one additional time.
Resolve the Bloodboil Sorcerer trigger from step 5, venturing into Undercity and completing Undercity.
Repeat from step 2.

Combos with "Bloodboil Sorcerer"