From Tobias:

“I have been seeding links to Vecna in my campaigns for two years. Now it’s finally time to pay it off by incorporating the newly released adventure Vecna: Eve of Ruin in my game. As a lead-up to this event I made this dungeon, which is occupied by the Cult of Vecna in one of the player character’s home town.

The dungeon itself has a prison area where some kidnapped victims are being held. The cultists have barricaded the southern corridor after a monster appeared from an adjacent cave in that area. The cave leads to the monster’s treasure hoard through the sewer – which the players could also use to traverse between grates scattered around the dungeon. Traversing the sewer could bypass some of the cultists, but doing so may result in a run-in with the creature…”