In a dank corner of the sewers there is a grate in the center of a great chamber. Steam vomits up from it; speak thy questions to it and the Oracle of the Vent may answer you, if your piety is great enough. If you do not know how pious you are, just as the milky Steam-Dryads that attend the Oracle. They can answer any questions you may have, as long as they pertain to the Oracle. What the Oracle actually is, is up to much debate. Probably something quite powerful.
The Muck Naga dwells near the sewer-shelf of the Dredge Lake, where it can way-lay the few who make the descent down to the sewers and attempt to befriend them. It has many ambitions, but its primary one is absolutely the safety of those who adventure down in the depths. It only wishes for your safety, it couldn't possibly bear to see more be devoured by the beasts of the sewers...
Down on the Dredge Lake, there is a small island with three small shrines, and three Naiad sisters, guardians of the Lake and attendants of the Lake God. The Lake God no longer hears their calls though, steeped as they all are in the filth that flows down from the city above. The sisters are getting desperate; soon their connection to the Lake God will sever completely. They need purity, and they need it soon.
The Dredge Lake is large, vaster than any surface surveyors might suspect. It has its own spirit; as all things sustained by the earth must, and it is large enough for its spirit to be a god. But it is old, and terribly confused. It has been corrupted by the flow of poison from the city above, and it is slowly dying, as the lake is. It cannot hear its attendants anymore, it can barely see the trolls that strike it with stone spears from their pile of filth. It is slowly losing its mind, and when it does, the lake will die with it.
It is not often that a Medusa will take up residence in a primarily human city; but this one has. By passing herself off as an eccentric artist, she maintains a partial presence in the city selling her unfortunate victims. She dwells bellow, in the sewers so that she does not petrify too many people; but she will do what she must to ensure that her deception remains undiscovered.
The Minotaur named Old Breakhorn by those who plumb the depths of the sewers has lived here now for two centuries, somehow. It inhabits a particularly poorly planned area of the tunnels, a crooked maze of passages and tunnels. No-one is quite sure how it has managed to survive this long; especially considering the number of adventurers who have brought back the Minotaur's head to the surface...
There have been legends of a Dragon dwelling 'neath the city of the Ives for long ages, but so far no one has actually seen it. Merely a myth, surely...
While probably not an actual demon, the Devil of the Southern Sewers has claimed enough lives in sufficiently brutal manner and numbers that it may as well be. Fiercely territorial, and aggresive beyond belief, no one is actually 100% sure what the Sewer Demon even is, the only consensus is that if you should ever come across it, you should run, and never look back. Even that would be enough for the beast to catch you.
Every city has its share of the vile and wicked. Few have on of such concentrated evil as the Ives. Beric has been known about for about a decade now in the seedier areas of the city (few as they are) and a reward has officially been put out for him. There is some doubt as to his existence though; no one has ever found him or his lair, no sign of it at all. Yet the half-chewed corpses of adventurers appear in the city squares overnight with enough regularity to suggest he remains still, watching from the shadows.
No-one is quite sure who the Cat-skin Knights are, why they are locked in their interminable struggle, or why they have come now to the city. Their struggle was the word of the day when they began their struggle in the city square before the Calico Knight fled down into the sewers, and the Piebald and Tortoise-Shell Knights ceased their quarrel to pursue it. Curiosity is a powerful thing, and the rumour-mills have presented many, many possible explanations for their combats.
The noble Hergault Assyrian once lived a dull and banally decadent life-style, until he discovered his tome of Necromancy. He couldn't rightly tell you where he found it, or how he came to be so devotedly sure of his ownership and mastery of it, but it is his now, and down in the secrecy of the sewers, he practices his black arts.
Unknown of the surface, the Slime-King holds his crown within his slopping and oozing body. Once it was merely another slime as any other, until it drained the powers of the crown (or more properly, the carnelian set in its apex) now resting within it. It dominates the slimes of the sewers near it now, and has carved out a rather nice little patch of tunnels for its lair, where it reigns with unthinking confidence.
Outcasts of Scudgen Isle, they have had no-where else to go other than the sewers. Technically brothers on their half-mother's father's side, they now only have each other, and that is grossly insufficient for them. They are not incredibly bright (even by troll standards) and they have only just been scraping by. They are scared, angry, and confused, in roughly equal quantities, and they are unlikely to survive in the long term.
Once, they were paladins, and a squadron of the Purifiers, but now, they have lost their memories, and they are also now lizard-men. Quite how this happened is beyond them, and all of them will adamantly refuse to admit the truth of their present situation, even to themselves.
And somewhere else in the sewers, there is a group of slain paladins, lying face-down in the muck, slowly decomposing...
It is pale and thin, flesh clinging only reluctantly to its bones and eyes sunken as far back from the light as its skull will physically allow. It is degenerate and wretched, and down here in the sewers, all it can do is crawl. However, it has managed, somehow to thrive; barely at least. It has utterly pacified a tribe of the Sewer-Troglodytes that haunt the tunnels, convinced them that it is their god, and now rules despotically from a particularly large chamber that it can sit on its haunches in, and gobble up the kills that the Troglodytes bring it. It is pleased with this arrangement, but it has earned itself a fair few enemies, least of all the other troglodyte groups of the sewers.
Hags are found in all sorts of places, and it should be no surprise that these three old crones have taken up residence in this caldera of corruption. Sister Gruel, Mother Splutter, and Granny Dross are their names, and they are not actually as hostile as one might expect. They are cruel mistresses of the local area, and few in the sewers dare earn their ire, but to surfacers, they are even a little bit friendly, ever willing to brew up a little something in return for the strange and unexpected prices they demand...
Hexaclaricus was not a particularly skilled mage. But, he got it into his head when he bound the demon Velcarinox to his service that he was an Archmage surely without compare, or so the demon said to him. Hexaclaricus set about immediately devising a method to distinguish someone to be a suitable apprentice to his readily apparent service, and so began construction on his 1000 trials (or rather, he set Velcarinox to constructing them. However, his lack of forethought mean that early on in construction he hit a series of natural caverns, and so gave up on the venture. Some of his goods are still secreted away within the testing chambers he did manage to erect though...
The Ives themselves were hardly the first to inhabit this land, as evidenced by the ancient crypts and tombs the sewers have had to incorporate into their design. Their culture can only be guessed at, their views and values only supposed. Hard evidence is hard to come by because of the sheer weight of the centuries scouring them from the records. Surely none could have possibly survived from those primeval days?
It used to actually be quite civilised in the Quiet Library, but as the city above grew and grew, so did the local water-table, and now the Quiet Library is the Sodden Library. An eclectic archive of esoteric secrets and literature, it has been slowly forgotten by those above, as it wished to be, and its curator and caretaker has toiled slowly and softly ever since, tending to the books, rotating them around and around the shelves so that the water damage is never too bad. Some usable tomes may yet remain...
A thorough-bred demon through and through, Grizzlesticks likes nothing more than massive, unbridled consumption. His table is set with everything and anything, as long as it is edible. Many are his "guests" whom are never permitted to leave, or stop eating. He himself is corpulent in the way the sea is really, really big, in the way that the moon is very, very far away, in the way that the sewers are very, very filthy. It is unlikely that he could even move if he ever wanted to without the assistance of a lot of magic. He may seem unthreatening, immobilised as he is, yet there is a deceptive power in his many flabby arms, and his words carry a magical force that is hard to resist. So far, there has been no break to his revelry for many, many years, despite many attempts to force the issue.
Slough used to be a man just like us, but a particularly unfortunate encounter with a Milk-Worm and a White Slime has left him less of a man than he used to be. His flesh is pale and soft, like cream cheese. Some of it slops off messily from time to time, and he must scrape what he can off the floor, mold it back onto himself, and hope that his regenerative abilities are as robust as he suspects. No longer admitted amongst the untainted above due to his condition, he is trapped below, and is understandably, a bit peeved about the whole situation. Very hard to permanently put down, his one remaining shred of sanity is focused wholly on finding a way to reverse what has happened, if one even exists within the labyrinth of the sewers...
A biomancer of some considerable skill, shunned from the city above, she dwells now in the clog, one of the more uninviting sections of the already hateful sewers. Her abominations are each lovingly tailored to be as fearsome as possible, and each are uniquely well suited to combat in the Clog. Her ambitions are limited not only to eternal life, and revenge on the city above, but also unlimited power, and potentially godhood, if she can swing it. She has not been able to make much progress whilst beneath, except that she is slowly, slowly amassing an army of abominations and flesh-servitors, built from the filth that freely flows from above.
The third of the sewers five resident wizards, Mary Cobbler has been quietly cultivating a grove of her own down in the depths when she can sneak away from her duties on the surface. She has become a mage of reasonable skill, but her true talents are in nurturing the plant-beasts she has been cultivating. They grow uniquely well on the foulness that flows through the sewers, and though it disgusts her to her core to utilise it, she would do anything for her "pets". She isn't quite sure what she is going to do with them when they are fully matured, but she is an impressionable sort. She'll find some sort of cause, one day; and knowing the Ives, left to her own devices, it won't be a good one.
There are few men as uniquely disquieting as Arnold Brecht, the Arachnomancer. His... obsession has consumed his life completely, and partly his flesh and form as well, and as such he was banished from the city above to the sewers below. This suited him just fine; while it was something of an inconvenience, he has flourished like never before in the darkness of the sewers. His hordes of loyal spiders have multiplied exponentially, and his research continues apace. He has no thoughts of recompense on his banishers, he merely wishes to continue as he is, down and down the path towards a pure predator...
The 6 vampires of the Sable Crown are all that is left of that vile court. Four young and two old vampires that managed to escape the Paladin's Purge of Blackstone, now driven to hide in the one place the Paladins would hesitate to chase them. They have set up a new "court" in a particularly dense and cut-off area of the sewers, where they continue their decadent orgies and salons, in as richly adorned chambers as they can manage, and given their talents, they have managed to steal quite a large amount from the city above during the night. Down below, when not consumed by revelry, they hunt as they please, unhindered by the light of the sun.
The unnamed King of All Toads and his Croaking Court have thrived as never before since they moved to the sewers of the Ives. They don't remain in one place for long, so as their few predators won't catch them, and that they don't completely deplete the local area of food. They are wise and considerate of their ecosystem, as a good court should be. They are also intolerant of trespassers on their territory, and will demand recompense from those that "transgress" their way. The Toad-Knights of the Croaking court are not particularly feared, but they should be. Ignorance is no excuse.
From down beneath. They know more than they say. They say much. Little of it is true. They are committed to spreading it. This is their purpose. The surfacers should no as much as possible. Then, they could not discern what is true from the false. They are beautiful so that you will not think wrongly of them. They bring gifts so that you will trust them. They are really so that if you learn the truth, you will not spread it. They have come to the sewers of the Ives so that they have a hidden lair. They will soon go to the city to spread their words. The people will learn much of the world beneath them. Our so they think.
The cold king has learned patience the hard way, through the long centuries he has spent frozen to his throne. He is a Death Knight of some startling power, and was much feared in his day. His day of course was long ago know, and only the more obscure texts will remember him; but there are some who hear his whispers in their dreams, and attend to him when they can. They move unseen and unharmed through the sewers, there are few that would risk raising the ire of a Death Knight against them, frozen as he is. They know it can't remain that way for long.