Preston, the Vanisher, Delney, Streetwise Lookout, Sefris of the Hidden Ways, and Veteran Dungeoneer

Prerequisites

• Preston, the Vanisher on the battlefield
• Delney, Streetwise Lookout on the battlefield
• Sefris of the Hidden Ways on the battlefield
• Veteran Dungeoneer in the graveyard

Steps

1. Complete a dungeon
2. Sefris' second ability triggers twice due to Delney
3. Resolve the first trigger, returning up to one other creature from your graveyard to the battlefield
4. Resolve the second trigger, returning Veteran Dungeoneer from your graveyard onto the battlefield
5. When Veteran Dungeoneer enters, it triggers once and Preston triggers twice due to Delney
6. Resolve a Preston trigger, creating a token copy of Veteran Dungeoneer that is a 0/1 Illusion
7. When the Veteran Dungeoneer token enters, it triggers twice due to Delney
8. Resolve the first Veteran Dungeoneer token trigger, venturing into Tomb of Annihilation and into the Trapped Entry room, causing each player to lose 1 life
9. Resolve the second Veteran Dungeoneer token trigger, venturing into the Oubliette room, causing you to discard a card and then sacrifice the nontoken Veteran Dungeoneer
10. Resolve the second Preston trigger from step 5, creating a token copy of Veteran Dungeoneer that is a 0/1 Illusion
11. When the Veteran Dungeoneer token enters, it triggers twice due to Delney
12. Resolve the first Veteran Dungeoneer token trigger, venturing into the Cradle of the Death God room, creating a 4/4 legendary The Atropal creature token and completing Tomb of Annihilation
13. If you control two or more The Atropal tokens, put all but one into your graveyard due to the legend rule
14. Repeat from step 2

Results

• Near-infinite lifegain triggers
• Near-infinite lifeloss
• Near-infinite lifeloss for all players
• Near-infinite sacrifice triggers
• Near-infinite ventures into the dungeon
• Return most creature cards from your graveyard onto the battlefield
• Cast a subset of spells in your library
• Near-infinite +1/+1 counters
• Near-infinite ETB
• Near-infinite LTB
• Near-infinite Treasure tokens
• Near-infinite card draw
• Near-infinite colored mana
• Near-infinite creature tokens
• Near-infinite death triggers
• Near-infinite draw triggers
• Near-infinite lifegain