The Void Market is a place for criminal activity beneath the Red Lantern District in an abandoned section of sewers. While the Undercity had been in use for a few months, it's fallen out of play for over a year. The existence of sewers, catacombs, and a set of ruins with buildings that are 2 to 3 stories high also didn't seem feasible to the ops. Basically, literal underground criminal activity still takes place in the Void Market rather than the Undercity. Thieves' Guild and Undercity wiki pages have been archived. Join the BDI Ops channel if you have any questions or concerns.
http://www.blkdragon.com/wiki/index.php ... oid_Market