Gulthirs were baatezu devils reduced to a ghastly, unclean form for failing their superiors and trapped in a punishment caste until they redeemed themselves. The gullet of a gulthir was certain doom for the baatezu that fell to it, for the wretched denizens of Hell embodied the two worst fears of devilkind—death and demotion.
Gulthirs towered at 10 ft (3 m) tall and appeared as skeletons with ruddy, sallow skin that hung loosely from their 800 lb (360 kg) bodies. Their bald, square, warty heads were covered in tumors and other lesions, and hosted two points of crimson light that were their eyes. The loose, oozing wounds that served as their mouths had jaws that could unhinge, allowing them to swallow man-sized prey with a single gulp.
Gulthirs lamented their current condition, universally and undoubtedly believing that they did not deserve their damnation. They loathed their forms and vented this hate on other devils, basking in the horror of others when they used their vile powers. They took every opportunity to abuse the remnants of their power and authority, and those that resisted their heavy-handed tyranny were swallowed, although transformation was only willingly used on greater fiends in a display of what pride they had left.
Clinging to what little they had and desiring even more, gulthirs kept treasure as a status symbol and adorned themselves with jewelry. They coveted objects of power, and kept the valuables of their victims within them for safe keeping.
A gulthir was a slow opponent whose primary weapon was its maw, with which it bit down on its enemies and swallowed them whole with ease, though they could only hold one creature in their gizzards at once. Those swallowed were immediately and irresistibly dominated by the gulthir, who could then take a few seconds to spew them out covered in slime. A thick white slime coated the victim's eyes, and once disgorged the dominated subject would have to either summon the willpower to shake off its influence, have someone else kill the gulthir, or have their eyes washed with holy water to escape its control.
Against fiends and other evil extraplanar beings, a gulthir had even more deadly options. If swallowed and lacking the fortitude to resist, the unfortunate fiend would be immediately destroyed, their essences absorbed to empower the gulthir to a degree matching the obliterated victim's vitality and strength. Instead of instantly ingesting a swallowed fiend, gulthirs could also slowly digest them in order to turn them into gulthirs as well.
Each day, gulthirs had a 75% chance to summon somewhere between one to four lemures. They could use the spell-like abilities greater teleport and see invisibility at will, and use ray of enfeeblement and scare fives times per day.
Having already lost so much, gulthirs charged recklessly into battle with little to fear. They chose an enemy and focused on trying to swallow that target as soon as possible, using scare to scatter other foes. They zapped stronger opposition with ray of enfeeblement to weaken them for when it came time to consume them, and summoned lemures when outnumbered as distractions (and to consume them to empower themselves).
Gulthirs were one of the forms a devil might take after enraging their masters through failure. Those that displeased their infernal overlords were often fed to gulthirs both to punish them specifically and to maintain the gulthir population. Lying outside the traditional hierarchy of Hell, gulthirs had to find some way to regain their master's confidence and/or favor lest they be condemned to an eternity as shadows of their former selves.
Ironically, despite being pariahs, their condition made gulthirs some of Hell's most loyal servitors, and they enjoyed the diversion of wreaking havoc on fiends below them. They acted as a kind of police force and living punishment, and other devils kept their distance as they went to work. When not serving a greater devil, they lurked Baator accruing lemure packs to serve as both pets and food, the lemures mindlessly milling about unaware of the dangerous situation they were in.
Gulthirs infested all the Hells, but were common on Dis, where Dispater would dispense his own paranoid form of justice. The creatures were all too frequent on the battlefields of the Blood Rift, serving as combination commissars and expendable shock troops. Pit fiends occasionally sent out squads of them to act as "press gangs" by hunting weaker yugoloths and turning the supposedly immortal fiends into gulthirs, bolstering the infernal forces without having to agree to hire the daemons as mercenaries. The greater devils would deny that the gulthir were working in any official capacity, but yugoloths killed them nonetheless whenever they could get away with it.
Newly formed gulthirs were rendered unconscious by the transformation, their bodies wracked with waves of agony as they adjusted to their new forms, and the moment they awoke, they knew all of their abilities, bodily functions, and what had to be done to escape them. Particularly old gulthirs were much larger than their newer counterparts, and could therefore swallow more sizable beings.
Least: Lemure • Nupperibo • Spinagon
Lesser: Abishai (Black • Blue • Green • Red • White) • Barbazu • Erinyes • Excruciarch • Ghargatula • Hamatula (Stony devil) • Kocrachon • Merregon • Osyluth • War devil • Xerfilstyx
Greater: Amnizu • Cornugon • Gelugon • Logokron • Narzugon • Orthon • Paeliryon • Pit fiend
Baatezu of unknown rank: Advespa • Dogai • Gulthir • Jerul
Araton • Burning devil • Fimbrul devil • Hellcat • Hellwasp • Imp (Bloodbag • Euphoric • Filth) • Kalabon • Kyton • Seared devil • Stitched devil • Succubus • Tar devil