Rumor speaks of a wizard’s guild, secretive and nameless, that manipulated peasant, merchant, and king alike from its underground school deep beneath the city. Entering and leaving through the sewer pipes, the wizards remained cloaked in mystery for years. One day, a civil war broke out among their ranks. An evil necromancer, cruel and hungry for power, attempted to take over the school. By the end of that day, every other member of the guild died rather than submit to his rule.
In time, the necromancer met his own special doom. Old age overtook him, and he wasted away in the solitude of his underground kingdom. As the end approached, the necromancer began working frantically, trying to discover the secret of lichdom before death took him. He conducted experiment after foul experiment, and the waste from these projects was casually dumped into the sewer or thrown into a shadowy corner. With the last of his strength, the necromancer stirred his iron cauldron, staring hopefully at the crimson goop bubbling within. Without warning, the goop slithered out of the pot and rushed up the old wizard’s arm, enveloping him, plugging his nose, and surging into his mouth. It clung to his skin like a coat of blood. In seconds, the necromancers wicked spirit flew howling into Acheron.
Most people in the city above were cozily ignorant of these events. Indeed, no one would have learned of the necromancer’s experiments had he been more tidy. As it was, decades of alchemic pollution had permanently altered the denizens of the sewers. They had become tougher, smarter, and almost immune to magic. The first sign of trouble was when the rats fled to the surface…

Necromantic Sludge is a black puddle of vile goo, an accidental byproduct of the necromancers experiments in the pursuit of extended existence. Rather than creating potions that could transform him into an undying lich, the necromancer ended up with this foul mess, which he dumped into the sewer.

Combat: Necromantic sludge can sense sentient humanoid life within 100 yards, and it attacks relentlessly with little regard for its own safety, seeking to feed on the life energy of its victims, This keen perception makes it impossible to surprise the monstrous goo. Necromantic sludge is poisonous to the touch, and casual contact inflicts 1 hp damage per round. In melee, the sludge lashes out with a pseudopod, inflicting 1d4+2 hp damage per successful strike. If the sludge slays an opponent, it attaches itself to the body to be absorbed through the skin, which turns dark gray within one round, regardless of the victim's original skin color. The body becomes a zombie in all respects, under the control of the sludge. After a few months, the decaying zombie body is discarded, unless a fresh body is encountered earlier. Necromantic sludge reflects spells as a ring of spell turning, except that it reflects 100% of a spell's or magical item's effect. The sludge is vulnerable to normal weapons, but magical attack and damage bonuses are not counted. In zombie form, the sludge sometimes employs a weapon, but like normal zombies, it inflicts 1d8 hp damage regardless of whether it uses a weapon.

Habitat/Society: Necromantic sludge exists only in the sewers, close to the old necromancer’s lair, but lately some has been ... (missing line) ... because of their singular behavior, but some speculate that they attack because of some nameless necromantic urge to destroy life. Others suggest that necromantic sludge attacks because of an urge to fulfill its “purpose” of bestowing undeath on its creator. Groups of necromantic sludge display some intelligence in the way they interact. They employ crude tactics sometimes, with one sludge lying still upon a sewer floor while in zombie form, with the others lurking nearby to attack when foolish intruders investigate the “corpse.”

Ecology: These monsters have little place in the noisome food chain of the sewers, since they can subsist only on humanoid lifeforce. They never bother mundane animals or other monsters, unless attacked. Since they are composed of magical, inedible slime, they are not themselves preyed upon by other spawn of the sewers.