Sefris of the Hidden Ways + Radiant Solar + Altered Ego + Omni-Changeling

Sefris of the Hidden Ways

Radiant Solar

Altered Ego

Omni-Changeling

How it works

1. Put any nontoken creature onto the battlefield.
2. When the creature enters, Radiant Solar, Altered Ego and Omni-Changeling each trigger.
3. Resolve the Radiant Solar trigger, causing you to venture into Tomb of Annihilation and into the Trapped Entry room, causing each player to lose 1 life.
4. Resolve the Altered Ego trigger, venturing into the Oubliette room, causing you to discard a card and then sacrifice Radiant Solar.
5. Resolve the Omni-Changeling trigger, venturing into the Cradle of the Death God room, creating a 4/4 legendary The Atropal creature token and completing Tomb of Annihilation.
6. If you control two or more The Atropal tokens, put all but one into your graveyard due to the legend rule.
7. Sefris' second ability triggers, returning Radiant Solar from your graveyard to the battlefield.
8. Repeat from step 2.

This intricate loop turns a single creature entering the battlefield into an explosive engine by rapidly traversing the Tomb of Annihilation dungeon. As Radiant Solar, Altered Ego, and Omni-Changeling all trigger upon entry, they cascade your dungeon progression through multiple rooms at once. Sacrificing Radiant Solar along the way sends it to the graveyard, which immediately satisfies Sefris of the Hidden Ways' condition to trigger her Create Undead ability. Once you complete the dungeon by invoking Omni-Changeling's copy effect to reach the Cradle of the Death God, Sefris resurrects Radiant Solar back onto the battlefield, letting you repeat the entire sequence indefinitely for near-infinite life loss and death triggers.