I would love that! Including more dragon heraldry symbols, if the artist is taking requests.

(I just noticed that this looks vaguely like the Starship Enterprise.)

In Level 5, purified water from Level 4 hits at a high spot that slopes both to the west and to the east. Water that flows to the west will reach the end of the canal and be deposited into water pipes that take it out to sea. Water that flows east will end up in a supersized drainage canal to help carry refuse from the bottom of the Great Maw.

The Great Maw ends at this level. All manner of waste digestible by the Black Pudding is tossed in here, including unusable metal and wooden objects, as well as any bones picked clean by the Gelatinous Cubes in Level 3. Here, the Black Pudding is munching on a great bell that has been thrown away, as well as some broken furniture. (Yeah, townfolk would probably chop up the broken furniture for firewood, but I wanted to show the Pudding eating metal and wood.) Left untouched for daring adventurers: a ceramic urn and a stone statue that are indigestible, along with some glass bottles. There’s also a staff, book, and scroll case that should be edible…unless they’re magical.

An extra large canal brings any remaining wastewater to the sea. Here, a Voracious Sullage has stretched itself across the canal, holding on to two side pillars as it scoops up anything edible remaining in the water.

A portion of the Great Maw’s wall has broken down, revealing a few caverns that are home to a strange tentacle aberration.

If adventurers survive the Black Pudding, the tentacle aberration, and the carnivorous plants down the passageway, they might find an escape route through the southern passage. But they might not be home free: something got the last adventurers who rested here (though that something might have been carbon monoxide poisoning if they lit a campfire in this poorly ventilated space).

Level 4 is the lowest level that maintenance workers generally go, though a stone door provides emergency access to Level 5 as needed. (Just realized I haven’t built that part yet.) Purified water from Level 3 flows through here. Luminescent Crystals are used to help keep the Black Pudding at bay. There is no access to the Great Maw from this level.

In Level 3, waste from the upper levels is purified through the strategic use of Gelatinous Cubes.

This level has the “nerve center” for the maintenance workers, where a number of wheel gate valves can be used to open or shut doorways in the canal drains, allowing portions of the treatment center to be closed off as needed, redirecting waste to open areas of the level.

Waste flows down to two great rooms, called Filtration Auditoriums. There, several Gelatinous Cubes gobble up as much of the waste as they can eat. The remaining waste flows through the Waste Filtration Path, where a series of grates keep four Gelatinous Cubes isolated. As oozes can slip through openings as small as an inch, these have been constructed to have mesh holes smaller than a quarter of an inch – small enough to allow water to flow through while keeping the Gelatinous Cubes contained, happily gobbling up a steady supply of food.

Wastewater flows through each Gelatinous Cube, becoming progressively more purified.

Each day, a passageway at the end of the Waste Filtration Path is opened, allowing the Cube at the end to crawl up a sloped path back to the Filtration Auditorium. (The stairs from Marine Dungeons help show how it slopes, and I included a spiral in the canal to show that as well.) As the Cube climbs the slope, it releases any indigestible objects along with now-purified water. Maintenance workers will then collect any coins or other valuables before tossing any remaining refuse into the Great Maw.

If a Filtration Auditorium needs to be closed (to retrieve a valuable object or for repair), there are two bypass lanes (one flowing down to the northern chamber, the other flowing down to the southern chamber) that can be opened as needed so that waste flows to the still-open auditorium. In addition, a passage that slopes up to the center and then back down to the other chamber connects the two chambers, allowing Gelatinous Cubes to be herded with bright lights to the other chamber.

QUESTIONS: I used Effluent 5 to show the most polluted sewage, and then down to Effluence 4 and then Effluent 3 as it was cleaned up. I then used the Water fill with varying levels of scum on top to show the water getting progressively cleaned. The more I look at Effluents 4 and 5, the more I’m wondering if I am using them as intended. Effluent 4 has a reddish hue – was it meant to be blood? And Effluent 5 is practically black. Is it meant to be some sort of demonic ichor or a necromancer’s waste? I’m wondering if it would be better for me to use Effluent 3 for the waste, and then the water fill with decreasing amounts of scum to show the water being cleaned?  

Still to come: I might need to add some arrows to show how things flow, and maybe more doors if certain areas need to be able to be bypassed. And more rocky terrain texture surrounding everything.

Although some outhouses and latrines are closed systems, some connect to canal drains in Level 2 of the town’s sewers. Stormwater drains from Level 1 help keep things flowing, but water from the town’s aqueducts is needed to supplement during dry weather. This level has wider walkways to make it easier for maintenance workers to address blockages and other problems.

Waste from here flows through chutes to Level 3.

Still to come: I may add some of the rocky texture to outline the canal drains on this level.