Last draft didn't work out as I wanted it to, so I put it on the backburner for now.
Underneath some undisclosed city, there's an enormous, biomechanical Sarlaac-like thing; or so the Foundation's seismological surveys estimate. It's somehow tapped into the underground networks of the city; it steals industrial sewage and runoff to use as stomach acid and runs organic tentacles into a nearby power plant to steal electricity to fuel its heart and brain. However, what makes it dangerous to the public is its methods of feeding- it extends enormous hollow tubes that look like subway tunnels into the local subway system, then diverts trains down its limbs into its stomach. Foundation operatives are forced to patrol the subways on a regular basis and dynamite shut any tunnels that shouldn't be there, all the while trying to figure out how to kill it without attracting attention/creating a massive sinkhole in the middle of town. Thoughts, ideas, questions, criticism are welcome.