Sorry for the delay with this.
I've got some stuff I need to figure out, so I've been trying to find time to reread stuff, but maybe it is better if I do my working out in public.
Things that PCs have to find out about, as the adventure progresses (in no particular order):
- Individual blockages in down-pipes will cause several knock-on problems (that the PCs will have to deal with/assist with) and all of these will be symptoms of the real cause of the problem,
- One problem will be the Deathwarden Dwarves threatening to take their own steps to preserve their own water supply (which might involve shutting off the flow of drinking water to surface dwellers or sealing down-pipes and causing surface toilets to overflow,
- Another problem might be one of the underground races thinking that sewage contamination in their water supply is an attack by surface dwellers who want to drive them out of the Undercity (they may "retaliate" by attacking sewer workers who are attempting to fix the problem),
- This problem started off - a long time ago - with the secret work of the Necromancers of Night Alley - they have been conducting illegal experiments where they attempt to use the power of Manifest and ectoplasm to animate the dead,
- The Necromancers of Night Alley have been hiding the evidence of failed experiments by rendering down dead bodies and body parts and flushing what is left down drains, but the drains were never designed for this,
- A fatberg started to forum below Night Alley and started to block the sewers from the city wall back to Night Alley,
- The fatberg contains various things, but one of the things that makes it different from other fatbergs is that contents include bones, strips of decomposed flesh enhanced with ectoplasm and necromantic magic,
- The fatberg carries some non-magical diseases,
- Parts of the fatberg function as ectoplasm and are edible to monsters that eat ectoplasm or ghosts,
- The fatberg is fairly sticky and can suck in people who try to walk on it or eat or remove parts of it,
- Monsters or ghosts who eat parts of the fatberg become contaminated with the diseases within the fatberg and can cause others to become ill.
Things that I need to check/clarify/develop:
- I think the river to the south of Manifest flows west to east, but need to confirm that (as the downhill direction is important),
- I know that Phantom Hill is fairly high up in the air, but have to get an idea of how high the various districts of Manifest are,
I know the first city of Manifest had a wall and that the current one only has fragments of that wall, so I need to decide how well the original sewers confirm to the map,
- I need to think about what security bars/features would be placed below a now gone city wall that might work as the starting point for a fatberg,
- I need to work out exactly where Night Alley is, and then work out how much of a blockage could be created between Night Alley and the lowest point of the first city of Manifest, where sewage would have flowed out through the city wall,
- I need to think about how drinking water gets into Manifest (considering that Manifest is 3 levels above the sewers and the sewers would have been just below ground level),
- I need to see if Ghostwalk canon has an underground river flowing into the Deathwarden Dwarven area and how the various other monsters would gain fresh water (considering that storm drains and sewers are two levels above some of these folks),
- I need to check the various living monsters in the two levels of the Undercity to see who would be affected by a sewer blockage and who might put aside differences with the PCs to work on a solution together. (I also need to figure out factions like undead that would be unaffected by sewage contaminating fresh water and who might try to take advantage of the situation.)
- I need to work out what sort of normal threats a fatberg can create,
- l need a cool name for one or more diseases that can be caught from the fatberg (or fatberg material),
- I also need to work out how a fatberg can work as a trap,
- I also need to work out what monsters can be trapped inside a fatberg and remain alive to attack anyone who digs them out.
So this is more of how the middle of the adventure will work.
Then I need to move onto what other factions would discover that a
magically enhanced fatberg has formed below Manifest and try to use the situation to their advantage.
I might go through all the standard factions and think about what their motivations would be.