Preston, the Vanisher, Delney, Streetwise Lookout, Sefris of the Hidden Ways, Ashnod's Altar, and Seasoned Dungeoneer

Prerequisites

• Preston, the Vanisher on the battlefield
• Delney, Streetwise Lookout on the battlefield
• Sefris of the Hidden Ways on the battlefield
• Ashnod's Altar on the battlefield
• Seasoned 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 Seasoned Dungeoneer from your graveyard onto the battlefield
5. When Seasoned Dungeoneer enters, it triggers once and Preston triggers twice due to Delney
6. Holding priority, activate Ashnod's Altar by sacrificing Seasoned Dungeoneer
7. Resolve a Preston trigger, creating a token copy of Seasoned Dungeoneer that is a 0/1 Illusion
8. When the Seasoned Dungeoneer token enters, it triggers twice due to Delney
9. Resolve the Seasoned Dungeoneer token triggers, venturing into Undercity twice
10. Resolve the second Preston trigger from step 5, creating a token copy of Seasoned Dungeoneer that is a 0/1 Illusion
11. Repeat steps 8 and 9 one additional time
12. Resolve the Seasoned Dungeoneer trigger from step 5, venturing into Undercity and completing Undercity
13. Repeat from step 2

Results

• Infinite +1/+1 counters on creatures you control
• Infinite ETB
• Infinite LTB
• Infinite Treasure tokens
• Infinite card draw
• Infinite colored mana
• Infinite colorless mana
• Infinite creature tokens
• Infinite death triggers
• Infinite draw triggers
• Infinite sacrifice triggers
• 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