After the intrepid explorers find the formerly sealed secret door they descend down into a small chamber using a ladder. That chamber is connected to a catacomb with 36 remaining alcoves for remains, four small doors to private burial chambers and a double door.
The walls weep. Now somewhat below the waterline of the bog-city of Sheljar there is a heavy amount of moisture, plus the southwest corner is open to the brackish waters of the area. Outside of the open pool are a large pile of bones. It is clear that the opening is natural, not manmade.
Possible learnings
Intelligence checks attempting to understand what could make such a large opening could use Nature, History, Culture (Sheljar) to understand that damage was done by a Tunneling Nightmare (DC 15).
Intelligence checks attempting to understand the alcoves and small doors could use Religion, Culture (Sheljar) to understand that the small doors are for former leadership of Sheljar (DC 10).
Inspecting the bones using Survival or Perception would find that they are recent to the area, not covered in dust (DC 10) and there are now 4 skeletons attacking the group.
Complications
If 50% of the group takes enough damage to fall unconscious making death saves the roar of a Tunneling Nightmare echoes, partially muffled by the water.
I’m doing Dungeon 23, but instead of making a megadungeon, I’m using it to expand my campaign world (some are calling this World23), but do so in a way that could be relevant to my players. I guess it will be a point-crawl-ish 23. Sometimes those points will be five-room dungeons. Sometimes they will be cities. There will always be paths between them, peoples population them, and peculiar memorable features.
What is Dungeon23?
Dungeon23 is a daily writing practice that is built around game design. Every day the participant will design another room in a dungeon, and at the end of the week they will have a complete level. The next week starts the process over until you have 52 dungeon levels. Sean McCoy of Tuesday Knight Games, the press behind the award-winning TTRPG, Mothership created the challenge almost on accident, with a tweet about his newest project and an image of his notebook. But the indie TTRPG scene is nothing if not excitable and easily swayed by a challenge, and McCoy’s personal goal quickly gained traction across Twitter.
Linda Codega in Gizmodo
Most importantly at Full Moon Storytelling, everything will be built with my players in mind (as SlyFlourish suggests for cities), because backstory without tablestory is a novel. The paths will help determine my next entry in Dungeon 23, the peoples (which could also include monsters) are created using my notecard NPS system, the peculiars are so that players have a hook to remember.
Full Moon Storytelling 