urban dungeon. Back in the 90's, I started a novel, The O Line, about some people like these and what they found in the New York subway, delving deep enough.
Naturally, I never finished it. Good to see the dungeoneering going on, though. Now let's just weird it up a notch ...
NEW YORK UNDERGROUND WANDERING ENCOUNTER TABLE
Roll 2d12, take the lowest. Add 1 to each roll for each additional level underground.
On active lines, trains come every 11-20 minutes. After midnight, 20% chance the train is a work train (some flatcars that can be jumped on), 5% chance it's the money train with 5-10 armed guards.
1: 2d8 workers
2: 1d4 transit cops
3: 1d8 homeless
4: 1d6 graffiti writers
5: Rat swarm
6: Bat swarm
7: 1d8 giant rats
8: 2d6 possessed/zombies/cultists
9: 1d8 ghouls
10: 1d4 giant albino sewer alligators
11: Ghost train (subway)/ ghost barge (sewers)
12: Giant slug
13: Purple worm
14: The Unnameable One