Stygian linnorms were massive, serpentine dragons without wings or hindlegs, with a pair of horns curling off of the crocodilian head. Their scales various shades of gray. The claws of the front legs, the only limbs linnorms had, were webbed.
Stygian linnorms were avaricious, cruel, and arrogant.
Stygian linnorms had very keen eyesight in addition to both darkvision and blindsight. They were immune to magic that induced sleep or paralysis, damage caused by acid, and anything that effected the mind; they were naturally immune to the forgetfulness effects of the River Styx. Stygian linnorms were also venomous, and their breath weapon was simply- and horrifyingly- a 60‑foot-long (18‑meter) cone of acid and Styx water that both damaged and potentially feebleminded enemies.
Additionally, Stygian linnorms had several spell-like abilities, able to cast fly and control water at will; dimension door, quickened enervation, feeblemind, and destruction each three times per day.
Stygian linnorms preferred to open combat by using enervation on the most obviously dangerous enemy, immediately followed by either their breath weapon (if against a group) or destruction (if against a single foe). They then go into melee, saving their spell-like abilities for enemies mobile enough to stay out of reach. Stygian linnorms only fought to the death when protecting their treasure, otherwise, they fled using dimension door if severely injured.
Stygian linnorms were native to and almost never found outside of the River Styx. They were generally solitary, although mated pairs and family groups of up to six were not unknown. They were also known ally with other powerful entities, acting as guardians, although even then they were near-impossible to control.
Chromatic dragons: Red • Black • Blue • Green • White • Brown • Gray • Purple • Pink • Salt • Yellow
Gem dragons: Amethyst • Beljuril • Emerald • Sapphire • Topaz • Crystal • Obsidian • Ruby
Neutral dragons: Amber • Jacinth • Moonstone • Pearl
Lung dragons: Chiang lung • Li lung • Lung wang • Pan lung • Shen lung • T'ien lung • Tun mi lung • Yu lung
Planar dragons: Adamantine • Astral • Battle • Blight • Chaos • Ethereal • Hellfire wyrm • Howling • Mirage • Oceanus • Pyroclastic • Radiant • Rust • Shadow • Styx • Tarterian
Epic dragons: Force • Prismatic
Catastrophic dragons: Earthquake • Volcanic
Miscellaneous dragons: Cobra • Dzalmus • Mist • Radiant • Rattelyr • Song • Vishap
Linnorms: Corpse tearer • Dread • Stygian
Drakes: Ambush • Black firedrake • Dragonne • Elemental (Earth • Fire • Ice • Magma • Ooze • Smoke • Water) • Felldrake (Crested • Spitting) • Greater • Guard • Mind • Portal • Rage • Space • Vulture
Dragonbloods: Draconic creature • Dragonborn of Bahamut • Dragonspawn
Drow-dragon (shadow) • Drow-dragon (deep) • Half-dragon • Kobold (Dragonwrought • Urd) • Weredragon • Zar'ithra • Zekyl
Hybrid monsters: Dracimera • Mantidrake • Wyvern drake