Another refugee from the Known World/Mystara, the decapus is ripe for reëxamination. Though it’s been around since—what, B3 Palace of the Silver Princess?—it’s never moved much beyond its “tentacled tree monster” archetype. The decapus’s shape recalls H. G. Wells’s The War of the Worlds; its preferred diet of gnomes points to an origin in the lands of the fey. At the very least, decapuses should be canny opponents who use their environment to the utmost advantage.
A strange underground mushroom forest is peopled by taciturn svirfneblin. Secretive even by the standards of their people, the gnomes hide a secret shame—they are all slaves, addicted to the cavern’s magical hallucinogenic fungi. Their masters are devious decapuses, who farm the gnomes like livestock, even as they squabble among themselves, splitting the forest into numerous small fiefdoms. They count on the svirfneblin and the cavern’s phantasm-creating mushrooms to shield them from intruders.
A saucer piloted by a decapus crashes into a forested ravine. The decapus quickly goes native, learning to hunt local game, but it is always on the lookout for magic and gems to repair the engine in its vessel.
The Canopy Realm boasts trees with trunks as broad as city blocks; they are so tall many of the Realm’s inhabitants have never set foot on land. In a world where the ground is a myth, decapuses are the Canopy Realm’s natural acrobats. Many take on the role of evil monks, seeking physical perfection and mental enlightenment while demanding offerings of meat (or convenient limbs) from supplicants wishing to learn their secrets.
—Pathfinder Bestiary 2 77