Preston, the Vanisher + Delney, Streetwise Lookout + Sefris of the Hidden Ways + Woe Strider + Rilsa Rael, Kingpin

Preston, the Vanisher

Delney, Streetwise Lookout

Sefris of the Hidden Ways

Woe Strider

Rilsa Rael, Kingpin

How it works

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 Rilsa Rael from your graveyard onto the battlefield.
5. When Rilsa Rael enters, it and Preston trigger twice due to Delney.
6. Holding priority, activate Woe Strider by sacrificing Rilsa Rael.
7. Resolve a Preston trigger, creating a token copy of Rilsa Rael that is a 0/1 Illusion.
8. When the Rilsa Rael token enters, it triggers twice due to Delney.
9. Resolve the Rilsa Rael token triggers, venturing into Undercity twice.
10. Resolve the second Preston trigger from step 5, creating a token copy of Rilsa Rael that is a 0/1 Illusion.
11. Repeat steps 8 and 9 one additional time.
12. Resolve the first Rilsa Rael trigger from step 5, venturing into Undercity and completing Undercity.
13. Repeat from step 2.

This intricate loop relies on Delney, Streetwise Lookout to supercharge Sefris of the Hidden Ways by doubling its completion triggers, allowing you to flood the board with creatures straight from the graveyard. Preston, the Vanisher seizes on these uncast entries to generate 0/1 Illusion copies of Rilsa Rael, Kingpin, whose own entry triggers are doubled by Delney to rapidly venture through and complete the Undercity dungeon over and over again. Meanwhile, Woe Strider acts as the crucial sacrifice engine that loops Rilsa Rael back into the graveyard while feeding the entire engine with the scry ability and its initial Goat token.