Cast Hostage Taker by paying its mana cost.
When Hostage Taker enters, it and Radiant Solar trigger.
Resolve the Hostage Taker trigger, exiling Rilsa Rael 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 Rilsa Rael to be returned to the battlefield from exile.
When Rilsa Rael enters, it and Radiant Solar trigger.
Resolve the Rilsa Rael 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 Rilsa Rael 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

Rilsa Rael, Kingpin

Cast Fiend Hunter by paying its mana cost.
When Fiend Hunter enters, it and Radiant Solar trigger.
Resolve the Fiend Hunter trigger, exiling Rilsa Rael.
Resolve the Radiant Solar trigger, venturing into the Oubliette room, causing you to discard a card and then sacrifice Fiend Hunter.
When Fiend Hunter dies, it triggers, returning Rilsa Rael from exile to the battlefield.
When Rilsa Rael enters, it and Radiant Solar trigger.
Resolve the Rilsa Rael 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 Fiend Hunter from your graveyard to the battlefield.
When Fiend Hunter enters, it and Radiant Solar trigger.
Resolve the Fiend Hunter trigger, exiling Rilsa Rael.
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 Fiend Hunter.
Repeat from step 5.

Fiend Hunter

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 Rilsa Rael from your graveyard onto the battlefield.
When Rilsa Rael enters, it and Preston trigger twice due to Delney.
Holding priority, activate Altar of Dementia by sacrificing Rilsa Rael.
Resolve a Preston trigger, creating a token copy of Rilsa Rael that is a 0/1 Illusion.
When the Rilsa Rael token enters, it triggers twice due to Delney.
Resolve the Rilsa Rael token triggers, venturing into Undercity twice.
Resolve the second Preston trigger from step 5, creating a token copy of Rilsa Rael that is a 0/1 Illusion.
Repeat steps 8 and 9 one additional time.
Resolve the first Rilsa Rael trigger from step 5, venturing into Undercity and completing Undercity.
Repeat from step 2.

Infinite artifact ETB

Infinite artifact LTB

Infinite artifact sacrifice triggers

Infinite artifact tokens

Infinite +1/+1 counters on creatures you control

Infinite creature ETB

Infinite creature LTB

Infinite Treasure tokens

Infinite card draw

Infinite colored mana

Infinite creature tokens

Infinite death triggers

Infinite draw triggers

Infinite mill

Infinite creature sacrifice triggers

Infinite self-mill

Near-infinite lifeloss

Put all basic lands from your library into your hand

Put all creature cards from your library onto the battlefield

Return most creature cards from your graveyard onto the battlefield

Preston, the Vanisher

Delney, Streetwise Lookout

Altar of Dementia

Combos with "Rilsa Rael, Kingpin"