Osyluths (pronounced: /ˈsilʌθsOSS-ee-luths[6]), sometimes called bone devils, served as taskmasters and interrogators of the devils. They act as law-enforcement throughout Hell, leading many devils to fear their presence. Bone devils delighted in torturing mortals and devils alike, causing physical and mental suffering wherever they go. Osyluths, along with hamatulas, made up the bulk of the Servants of Mammon, Mammon's personal army.[7]


Osyluths' form were bony. They were thin and had a scorpion-like tail.[8]

An osyluth stood about 2.74m (9ft) tall and weighed roughly 227kg (500lbs). Osyluths often served as the informers and police of the Nine Hells, monitoring and reporting on the activities of other devils.[3]


When an osyluth was promoted to an amnizu, it underwent a process that was potentially lethal. The process consisted of racking, drawing, and quartering. When the osyluth got quartered, it naturally lost its limbs, but new smaller ones regrew. Once every limb was gone and replaced with a smaller one, the skin of the face was peeled to create a cowl that the would-be-amnizu had to remove through will-power, lest it died.[9]


Osyluths fulfilled the role of a police force in Baator. They actually liked their job.[8]

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Osyluths fought with their claws, fangs, and their tails. The scorpion-like tail was actually poisonous, which was sapped the strength of the victim.[8]

They had a number of magical abilities. They could surround themselves with an aura that affected their enemies within 5 feet (1,5 meters) with an effect that was similar to the fear spell. Other innate spells they could cast were improved phantasmal force, invisibility, and wall of ice. They could also summon aid once per day, they had various options to do so. They could summon up to hundred nupperibos, an ability that only worked half the time or up to two osyluths with a 35% chance of success.[8]

Osyluth had the necessary mental capacity to learn the art of a wizard. They had a talent for divination. They used this magic to aid themselves at their job. However, osyluths who actually cared to learn the craft were rare. Another branch of magic osyluths pursued was that of divine magic tied to a deity. The overall numbers of such priests was small, but osyluths were a substantial group among them. When they practiced divine magic tied to a deity, they were always specialty priests.[10]

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Learn to love and uphold the law.
— The "lesson" an osyluth needed to learn for promotion.[11]

Osyluths fulfilled a function similar to a police force in Baator.[8] To be more precise, they were a moral police who looked out for moral decay in the infernal society. Devils who were not upholding the ideals of the lawful evil philosophy were captured and punished by them. This, meaning the prospect of punishment not the supervision itself, was the reason why other devils hated and sometimes killed osyluths, the latter only under utmost secrecy.[11] They were even allowed to drop offending devils, with the notable exception of pit fiends, into the Pit of Flame.[12]

Every century, one thousand osyluths were promoted at once to the hamatula-station and one thousand low-ranking devils were promoted to osyluths to fill the gap. Nobody really knew how, but this fact got somehow distorted when it reached mortals, making them believe for a long time that the entirety of Baator held only a thousand osyluths.[11]


Pool of Twilight

The warrior Kern Desanea battling an osyluth, as depicted on the cover of the novel Pool of Twilight.

The famed Paladin Kern Desanea, the "Hammerseeker", fought with an osyluth during his adventures in the Moonsea region.[citation needed]

A mage from Dweomercore named Yarek summoned a bone devil to kill a rival, Skrianna Shadowdusk. The osyluth agreed, but then murdered him, while still seeking to fulfill it's contract.[13]






  1. 1.0 1.1 1.2 Wizards RPG Team (2014). Monster Manual 5th edition. (Wizards of the Coast), pp. 68, 71. ISBN 978-0786965614.
  2. Mike Mearls, Stephen Schubert, James Wyatt (June 2008). Monster Manual 4th edition. (Wizards of the Coast), p. 61. ISBN 978-0-7869-4852-9.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 Skip Williams, Jonathan Tweet, Monte Cook (July 2003). Monster Manual 3.5. (Wizards of the Coast), pp. 52–53. ISBN 0-7869-2893-X.
  4. Allen Varney, ed. (June 1994). Planescape Monstrous Compendium Appendix. (TSR, Inc.), p. 27. ISBN 978-1560768623.
  5. Gary Gygax (December 1977). Monster Manual, 1st edition. (TSR, Inc), p. 21. ISBN 0-9356-9600-8.
  6. J. Paul LaFountain (1991). Monstrous Compendium: Outer Planes Appendix. Edited by Timothy B. Brown. (TSR, Inc.), p. 5. ISBN 1-56076-055-9.
  7. Monte Cook (Oct 2002). Book of Vile Darkness. (Wizards of the Coast), p. 150. ISBN 0-7869-0672-3.
  8. 8.0 8.1 8.2 8.3 8.4 Chris Pramas (1999). Guide to Hell. (TSR, Inc.), p. 62. ISBN 978-0786914319.
  9. Colin McComb (September 1997). Faces of Evil: The Fiends. Edited by Ray Vallese. (Wizards of the Coast), p. 17. ISBN 0-7869-3430-1.
  10. Chris Pramas (1999). Guide to Hell. (TSR, Inc.), pp. 57–58. ISBN 978-0786914319.
  11. 11.0 11.1 11.2 Colin McComb (September 1997). Faces of Evil: The Fiends. Edited by Ray Vallese. (Wizards of the Coast), p. 16. ISBN 0-7869-3430-1.
  12. Chris Pramas (1999). Guide to Hell. (TSR, Inc.), p. 32. ISBN 978-0786914319.
  13. Christopher Perkins (November 2018). Waterdeep: Dungeon of the Mad Mage. Edited by Jeremy Crawford. (Wizards of the Coast), p. 134. ISBN 978-0-7869-6626-4.

Least: AdvespaLemureNupperibo
Lesser: AbishaiBarbazuHamatulaSpinagon
Greater: AmnizuCornugonErinyesGelugonOsyluthPit fiendWar devil
Miscellaneous Devils
Alu-fiendArchdevilCambionDuergarFimbrul devilHellcatImpKytonSeared devilSuccubusTar devil
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