Radiant Solar + Sefris of the Hidden Ways + Barrowin of Clan Undurr + Mardu Siegebreaker

Decks

How it works

Cast Mardu Siegebreaker by paying its mana cost.
When Mardu Siegebreaker enters, it and Radiant Solar trigger.
Resolve the Mardu Siegebreaker trigger, exiling Barrowin of Clan Undurr until Mardu Siegebreaker leaves the battlefield.
Resolve the 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 Barrowin of Clan Undurr to be returned to the battlefield from exile.
When Barrowin of Clan Undurr enters, it and Radiant Solar trigger.
Resolve the Barrowin of Clan Undurr 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 Barrowin of Clan Undurr 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.

In which brackets is this combo allowed, per Spellbook's Exhibition tier?

1–2 · Exhibition & Core

Allowed in this bracket.

3 · Upgraded

Allowed in this bracket.

4–5 · Optimized & cEDH

All combos are allowed.

How it works

Cast Mardu Siegebreaker by paying its mana cost.
When Mardu Siegebreaker enters, it and Radiant Solar trigger.
Resolve the Mardu Siegebreaker trigger, exiling Barrowin of Clan Undurr until Mardu Siegebreaker leaves the battlefield.
Resolve the 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 Barrowin of Clan Undurr to be returned to the battlefield from exile.
When Barrowin of Clan Undurr enters, it and Radiant Solar trigger.
Resolve the Barrowin of Clan Undurr 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 Barrowin of Clan Undurr 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.