[Commissioned by @glarnboudin. The original image was posted to Twitter, possibly as part of the #buildabetterfaketheropod movement, but appears to have been deleted. The little horns got me thinking “devil dinosaur”, and then it kept going. In the Pathfinder setting, my favorite daemonic harbinger is Deceid, the lord of invasive species and ecosystem collapses. I think he had a hand in these guys’ creation.]
Stygionyx CR 15 NE Magical Beast This massive reptile looks like a cross between a dinosaur and a crocodile, with white eyes and a pair of horns over its fanged maw. A jagged ridge grows along its back, and its long arms end with scythe-like claws.
Even the Outer Planes can suffer the effects of invasive species. Dinosaurs are not uncommon in the Abyss, particularly with the fiendish template, as various demon lords maintain primeval aspects to their layers or count reptilian humanoids as their worshippers. Among the carnivorous dinosaurs, the spinosaurus is one of the largest and most resilient, and they eventually escaped into the River Styx. Rather than being locked into a fugue state and becoming just another casualty of that mighty river, they were molded into even more fearsome semiaquatic predators. Stygionyxes now patrol all of the Lower Planes, seeking to make petitioners and fiends alike into toothsome snacks.
A stygionix is sapient, but they act much as their animal ancestors did, as ambush predators of waterways. Their claws and teeth pass through the hides of fiends with ease, and they radiate an aura that makes teleportation impossible. Once combat is joined, they will often fight until slain, still thrashing and slashing to the bitter end.
Acclimation to the River Styx has granted stygionyxes immunity to all manner of mind influencing effects and spells, making them difficult monsters to control. They can be negotiated with, but their single minded dedication towards hunting and eating leaves little room for compromise. Some fiends turn them against their enemies with promises of novel delicacies (such as celestial beings or mortals), or merely lure them into positions where their depredations can play a purpose. Fiendish warriors of many species hunt them for trophies or sport, but the hunter frequently ends up the hunted.
A stygionyx grows more than fifty feet long. The oldest specimens can live for a century.
