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Ydersius's unholy symbol.

The Headless King, Lord of Coiling Poison, the Father of Serpents, the Primal Coil, the Sundered God, the Slumbering Speaker Below, the Severed God
Areas of Concern
Seek to return Ydersius to life
Fulfill your passions
Conquer your foes with no mercy
Achieve glory for serpentkind
Put the needs of others above those of serpentfolk
Aid the spawn of Azlant
Cleric Alignments (1E)
Domains (1E)
Chaos, Evil, Nobility, Scalykind, War
Subdomains (1E)
Demon, Leadership, Martyr, Saurian, Tactics
Cleric Alignments (2E)
Domains (2E)
Ambition, Indulgence, Might, Zeal
Favored Weapon
Snake skull and ouroboros
Sacred Animal
Sacred Colors
Green, red
Source: Sanctum of the Serpent God, pg(s). 66ff.1E
Pathfinder Bestiary 2, pg(s). 237
Avatar of Ydersius

(chaotic, evil, extraplanar)
Source: Sanctum of the Serpent God, pg(s). 54

The ancient deity Ydersius (pronounced yeh-DER-see-us)1 is the patron of the serpentfolk, a race of snake-like monstrous humanoids who battled humans of ancient Azlant during the Age of Legend.2 A deity of unquenched passion and anger, the generally more cerebral serpentfolk used him as an example of all that was potent and primal in their psyche.3


In the Age of Serpents, Ydersius walked among his people as the embodiment of their might and power, commanded their armies to countless victories, raised great cities, and sired semi-divine offspring who ruled in their father's name.4

In one of the final battles of the war between the serpentfolk and the Azlanti, the mighty Azlanti champion Savith led an army to the depths of Garund and decapitated Ydersius in his hallowed sanctum of Ilmurea. However, Savith was unable to kill Ydersius. She threw his headless body to the lightless Darklands deep below, and cast his still-conscious skull into a lake of fire, before succumbing to his venom. His clerics still receive divine magic, a sure sign that he has not followed Aroden into true death.354

Although he was not yet dead, Ydersius' defeat marked the terminal decline of the serpentfolk empire. However, the serpentfolk have survived, and they vow to restore the Headless King. They believe that should his body and head be reunited, Ydersius would return to full power and lead his people in an attack against the surface world.46

According to the ancient legends of the Mwangi, the Zenj folk hero Old-Mage Jatembe learned secrets from the severed head of Ydersius before sewing its lips shut.78


Yderius once made his home in Sydrixus, a pocket plane within the Maelstrom near the border with the Outer Rifts. He has not returned there since his defeat, and Sydrixus is no longer accessible to his servants; it is unknown if this place still exists anymore.910


Ydersius takes the form of a giant, muscled serpentfolk with an impossibly long tail, adamantine-hard scales, and iron-like fangs. Ydersius is famous for his threefold poison: fang venom, toxic blood, and a cloud of poison exuded from his body. Statues often depict him standing on a pedestal made from the coils of his tail, and wearing an elaborate crown or headdress, although his clothing is simple.4

Ydersius' headless body now mindlessly rampages through the depths of Orv, while his skull still lies in the cooled lava lake near Ilmurea where Savith disposed of it, luring serpentfolk to that region and sending them visions and thoughts. Having been divided in two for so long, Ydersius is scarcely conscious or aware of his own followers, and his communions with them are confusing and often conflicting.41112

Avatar of Ydersius

Ydersius' avatar resembles the full god: it is a huge snake-headed humanoid with a massively long tail.4


Since his fall, no gods have had relationships with Ydersius. Prior to his fall, the pantheon of Azlant led by Abadar, Desna, and Shelyn stood together against the Father of Serpents, and it is extremely likely that these three gods would re-engage their battle against a resurgent Ydersius. He has also long been opposed to Yig, who has turned his attentions elsewhere after Savith defeated Ydersius.1314

Another enemy of Ydersius was the demon lord Abraxas whose portfolio includes snakes. This initiated a clash of power over the serpentfolk population dear to Ydersius. Some serpentfolk still worship Abraxas, and the cult of Ydersius does not tolerate such heresy.13


All of the god's servants are ophidian. Ydersius' herald is known as the Emperor of Scales.15

Three other servants are commonly known within the cult:13

Church of Ydersius

Ydersius is the patron deity of the serpentfolk, who are his still-active mortal kin. An organization exists known as the Coils of Ydersius that is dedicated to bringing about his triumphant return. At the height of their empire, the serpentfolk venerated Ydersius as the paragon of their species and embodiment of their eternal empire. Since his defeat, the degenerate serpentfolk have worshipped him as their progenitor and a god of war and poison; while the few remaining advanced serpentfolk see him as the one who would revive the old serpentfolk empire.1617 The cleric Vyr-Azul is particularly fanatical about restoring Ydersius and the serpentfolk empire.18

In addition to serpentfolk, Ydersius is also worshipped by a few iruxis, boggards, and xulgaths as a god who will bring their species back to their old glories. He is also venerated by some nagas and sorcerers as a god of snakes, by human snake cults as a god of immortality, and by fringe assassin groups as a god of poison and murder.17

Unholy Texts

Many unholy texts of Ydersius were lost when the serpentfolk empire fell, including the Alberos Analects.19 Today, only the Sekamina Destinies are used by cults.13


The faithful of Ydersius once celebrated many holidays, but today only one date has much significance: the Day of Sundering on 29 Rova.19


The Skull of Ydersius, a powerful artifact, can be attached to his headless body to allow him to return to full power. Destroying it would permanently kill Ydersius, but this is an almost impossible task. For instance, one method requires Ydersius' manifestation to be dragged to the Boneyard and slain in the presence of Pharasma for her immediate judgment, which would cause him to disintegrate.202122


Paizo published a major article about Ydersius in Sanctum of the Serpent God 66ff.

For additional as-yet unincorporated sources about this subject, see the Meta page.

  1. Erik Mona, et al. “Appendices” in Campaign Setting, 247. Paizo Inc., 2008
  2. Sean K Reynolds, et al. Inner Sea Gods, 192. Paizo Inc., 2014
  3. 3.0 3.1 Sean K Reynolds. “Other Gods” in Gods and Magic, 52–53. Paizo Inc., 2008
  4. 4.0 4.1 4.2 4.3 4.4 4.5 Robert G. McCreary. Ydersius” in Sanctum of the Serpent God, 67. Paizo Inc., 2011
  5. James Jacobs & Greg A. Vaughan. “Bestiary” in Into the Darklands, 57. Paizo Inc., 2008
  6. James Jacobs, et al. The Inner Sea World Guide, 235. Paizo Inc., 2011
  7. Amber Stewart, et al. “Mwangi Campaigns” in Heart of the Jungle, 41. Paizo Inc., 2010
  8. Kyle Baird. The Technic Siege, 6. Paizo Inc., 2014
  9. Jesse Benner, et al. “Bestiary” in Sanctum of the Serpent God, 83. Paizo Inc., 2011
  10. Robert Brookes, et al. “Chapter 3: The Great Beyond” in Planar Adventures, 186. Paizo Inc., 2018
  11. Amber Stewart, et al. “Life in Mwangi” in Heart of the Jungle, 15. Paizo Inc., 2010
  12. Neil Spicer. “Sanctum of the Serpent God” in Sanctum of the Serpent God, 53. Paizo Inc., 2011
  13. 13.0 13.1 13.2 13.3 Robert G. McCreary. Ydersius” in Sanctum of the Serpent God, 71. Paizo Inc., 2011
  14. James Jacobs. “The Elder Mythos” in In Search of Sanity, 73. Paizo Inc., 2016
  15. Jesse Benner, et al. “Bestiary” in Sanctum of the Serpent God, 82. Paizo Inc., 2011
  16. Erik Mona, et al. “Chapter 5: The World” in Campaign Setting, 198. Paizo Inc., 2008
  17. 17.0 17.1 Robert G. McCreary. Ydersius” in Sanctum of the Serpent God, 68. Paizo Inc., 2011
  18. Neil Spicer. “Sanctum of the Serpent God” in Sanctum of the Serpent God, 7–8. Paizo Inc., 2011
  19. 19.0 19.1 Robert G. McCreary. Ydersius” in Sanctum of the Serpent God, 70. Paizo Inc., 2011
  20. F. Wesley Schneider. “Legendary Artifacts” in Artifacts & Legends, 48. Paizo Inc., 2012
  21. James Jacobs. “Beyond Serpent's Skull” in Sanctum of the Serpent God, 60. Paizo Inc., 2011
  22. James Jacobs. “Beyond Serpent's Skull” in Sanctum of the Serpent God, 61. Paizo Inc., 2011