Todd Stewart’s The Great Beyond introduced us to proteans—the serpentine creatures of chaos that have replaced the world’s oldest role-playing game’s slaadi. Organized (though they would bristle at the term) into castes and choirs, these creatures work to spread disorder and entropy throughout the universe. Surrounded by telepathic whispers, imentesh proteans are manipulators behind the scenes—treacherous Iagos equally determined to recreate the social and literal landscapes of the mortal world.
A mystic theurge is tricked by an imentesh masquerading as a divine herald and muse. Under the protean’s sway, the theurge begins to make erratic but brilliant leaps forward in his studies. In reality, the imentesh’s telepathic whispers are teaching theurge the rites to unleash an aeon upon his orderly, unsuspecting world.
The rise of a burgeoning middle class in Lochland has resulted in a new innovation: public museums. A month of sell-out crowds draws the attention—and then ire—of an imentesh, who is appalled by the museum complexes’ aim of cataloging and ordering knowledge. Employing its various spell-like abilities overnight with abandon (polymorphing, shrinking, and shattering some objects, while restoring and warping others with make whole and major creation), it seeks to turn the museum into a funhouse of chaos.
The imentesh Kemosh loves using honeyed words and wild warpwave strikes to undermine the resolve, intellects, and bodies of mortal religious leaders, philosophers, teachers, and sensei—sabotaging duelists and monks before a public bout, or sapping the will of a great debater just before an election. Then again, if one of his warpwave ripples causes greater disruption—such as the elven pope he happened to baleful polymorph into a ferret—so much the better.
—Pathfinder Bestiary 2 214
Proteans are a vast improvement on slaadi. Despite being Fiend Folio classics, slaadi just don’t have the philosophical heft required to be real representatives of disorder—their approach to chaos inevitably boils down to: “Shall I eat you now or later?” (Plus, all they do is hang around the Spawning Stone like surly teenagers outside a Wawa.) The tribal, inscrutable choirs of the keketars appeal to me far more.
That said, I remember there being a decent Alien-style adventure based around a red slaad in an old 2e Dungeon, and an article on the slaad lords in Dragon Magazine around the time Planescape came out. If I run across them, I’ll post the issue numbers and details.
The Dungeon Adventure you were wondering about with the Red Slaad chestburster is “Jacob's Well” from Dungeon 43. Definitely a classic.
It's actually the first adventure I ever ran, watching my giggling preteen classmates spiral slowly into paranoia. Good times, good times.