Radiant Solar + Sefris of the Hidden Ways + Glorious Protector + Passageway Seer

Radiant Solar

Sefris of the Hidden Ways

Glorious Protector

Passageway Seer

How it works

1. Cast Glorious Protector by paying its mana cost.
2. When Glorious Protector enters, it and Radiant Solar trigger.
3. Resolve the Glorious Protector trigger, exiling Passageway Seer until Glorious Protector leaves the battlefield.
4. Resolve the Radiant Solar trigger, venturing into the Oubliette room, causing you to discard a card and then sacrifice Glorious Protector.
5. Glorious Protector leaves the battlefield, causing Passageway Seer to be returned to the battlefield from exile.
6. When Passageway Seer enters, it and Radiant Solar trigger.
7. Resolve the Passageway Seer 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 Glorious Protector from your graveyard to the battlefield.
10. When Glorious Protector enters, it and Radiant Solar trigger.
11. Resolve the Glorious Protector trigger, exiling Passageway Seer until Glorious Protector 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 Glorious Protector.
14. Repeat from step 5.
15. Cast [[Permanent with ETB: "Exile a creature" and LTB: "Return exiled creature to BF" (Banish Creature)|banisher]] by paying its mana cost.
16. When Glorious Protector enters, it and Radiant Solar trigger.
17. Resolve the Glorious Protector trigger, exiling Radiant Solar and two other nontoken creatures until Glorious Protector leaves the battlefield.
18. Resolve the Radiant Solar trigger, venturing into the "Sandfall Cell" room, causing you to sacrifice Glorious Protector and each opponent to either sacrifice a creature, artifact or land or lose 2 life.
19. Glorious Protector leaves the battlefield, returning Radiant Solar and the two other nontoken creatures from exile to the battlefield.
20. Radiant Solar and the two creatures enter the battlefield, triggering Radiant Solar three times.
21. Resolve the first Radiant Solar trigger, venturing into the "Cradle of the Death God" room, creating a 4/4 The Atropal legendary creature token, and completing Tomb of Annihilation.
22. Sefris' second ability triggers, returning Glorious Protector from your graveyard to the battlefield.
23. When Glorious Protector enters, it and Radiant Solar trigger.
24. Resolve the Glorious Protector trigger, exiling Radiant Solar and two other nontoken creatures until Glorious Protector leaves the battlefield.
25. Resolve the Radiant Solar trigger, venturing into the "Trapped Entry" room of the Tomb of Annihilation, causing each player to lose 1 life.
26. Resolve the second Radiant Solar trigger from step 6, venturing into the "Veils of Fear" room, causing each player to lose 2 life unless they discard a card.
27. Repeat from step 4.

This intricate loop leverages Sefris of the Hidden Ways as its cornerstone, using her graveyard-trigger prowess to transform dungeon exploration into a continuous engine of recursion. By cycling Glorious Protector in and out of play, you repeatedly trigger Radiant Solar to race through dungeons at breakneck speed. Passageway Seer can assist in kicking off the momentum by taking the initiative, while Radiant Solar's own sacrifice mechanics feed Sefris's ability to pull Glorious Protector right back from the graveyard, creating a self-sustaining loop that infinitely repeats entry and exit triggers.