Preston, the Vanisher, Delney, Streetwise Lookout, Sefris of the Hidden Ways, Aarakocra Sneak, and Phantom Train

Prerequisites

• Preston, the Vanisher on the battlefield
• Delney, Streetwise Lookout on the battlefield
• Sefris of the Hidden Ways on the battlefield
• Aarakocra Sneak in the graveyard
• Phantom Train on the battlefield

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 Aarakocra Sneak from your graveyard onto the battlefield
5. When Aarakocra Sneak enters, it and Preston trigger twice due to Delney
6. Holding priority, activate Phantom Train by sacrificing Aarakocra Sneak
7. Resolve a Preston trigger, creating a token copy of Aarakocra Sneak that is a 0/1 Illusion
8. When the Aarakocra Sneak token enters, it triggers twice due to Delney
9. Resolve the Aarakocra Sneak token triggers, venturing into Undercity twice
10. Resolve the second Preston trigger from step 5, creating a token copy of Aarakocra Sneak that is a 0/1 Illusion
11. Repeat steps 8 and 9 one additional time
12. Resolve the first Aarakocra Sneak 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 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