Radiant Solar trigger, venturing into the Oubliette room, causing you to discard a card and then sacrifice
Mardu Siegebreaker.
Mardu Siegebreaker leaves the battlefield, causing
White Plume Adventurer to be returned to the battlefield from exile.
When
White Plume Adventurer enters, it and
Radiant Solar trigger.
Resolve the
White Plume Adventurer 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
Mardu Siegebreaker from your graveyard to the battlefield.
When
Mardu Siegebreaker enters, it and
Radiant Solar trigger.
Resolve the
Mardu Siegebreaker trigger, exiling
White Plume Adventurer until
Mardu Siegebreaker 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
Mardu Siegebreaker.
Repeat from step 5.
Results
Near-infinite ETB.
Near-infinite LTB.
Near-infinite lifeloss for all players.
Near-infinite sacrifice triggers.
Near-infinite death triggers.
Metadata
In 17 decks according to EDHREC.
Bracket Tag
This combo has been estimated to be Exhibition (Bracket 1+).