Part humanoid, part swarm; nearly undead, yet literally squirming with life—the worm that walks is literally a walking contradiction. It’s also one of the standout monsters of the Bestiary 2, instantly recognizable as it perfectly straddles the line between fantasy and true horror.
According to Amanda Hamon’s “Ecology” in Pathfinder Adventure Path #75: Demon’s Heresy, worms that walk have popped up everywhere from Lovecraft to Buffy. (My favorite example is The Hooded One from Jeff Smith’s Bone). They have featured prominently in several Adventure Paths, especially Dungeon’s Age of Worms and the recently completed Wrath of the Righteous. And, as I just mentioned, Demon’s Heresy serves up a very nice ecology with several example NPCs and variants.
So rather than retread that ground, I instead just want to take a moment to discuss the difference between worms that walk and liches.
Despite its fearsome reputation and the risks involved in its pursuit, lichdom is, at its core, a conservative existence. It’s an insurance policy for those mages who don't have the tools or talent to achieve immortality in life. A lich’s originating impulse is the desire to cheat death, and every other goal they work toward—greater magical might, domination over a kingdom, divine status, you name it—is secondary to that.
Becoming a worm that walks, on the other hand, is a Hail Mary play. It’s difficult to become one intentionally—doing that involves actually dying and burial in vermin-infested unholy ground. So most worms that walk arise spontaneously, out of a confluence of environmental evil, luck, and their own indomitable wills. It's what happens when a spellcaster is so obsessed with his goals that death itself becomes a mere speed bump.
All of which means that worms that walk are not going to hide in a deathtrap-filled dungeon or deep under a secret library the way a lich might. The worm’s very existence is a miracle. Every worm that walks, whether generated spontaneously or via careful preparation, knows with absolute certainty why he or she was spared death’s embrace. The worm that walks walks for a reason; it is a creature actively pursuing its goals and ambitions. It has plans—big ones—and gods help the PCs who get in the way.
The man who would become Rancor’s Embrace left nothing to chance when he became a worm that walks. He buried himself alive in a potter’s field reserved exclusively for tieflings, using his last telekinesis to cover himself and consign his body to death. Now returned as a scuttling mass of beetles, he intends to kill every last one of the Maimed Maiden’s priestesses for helping his wife to flee with his infant child.
Yertham Mar died at sea, but his spirit returned in an amalgam of worms, minute crabs, and a thousand other oozing, wriggling creatures. Barely able to hold himself together above water, he should nevertheless be feared. The crustaceans that compose his body hunger for flesh more than the average worm that walks, and they strip away meat every time they engulf someone (consider the engulf damage to be one Hit Dice category higher and normal).
While undeath is abhorrent even to evil druids, becoming a worm that walks sometimes holds a macabre appeal. Reese o’ the Wildwood still thinks of himself as a defender of the forest, despite his wriggling shape. But his obsession with reanimating pixies, wolves, and bugbears as undead shows that his power now stems from some other unnatural source.
—Pathfinder Bestiary 2 286–287
Work is kind of crazy, but rest assured I’m still reading all your comments, messages, and reblogs. Also, just finished Scott Lynch’s The Lies of Locke Lamora. Pretty great! If you like heists and thieves’ guilds, I recommend it.