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Horned Serpent

This huge snake has a pair of wide horns, like those of a bull, and a smooth, opaque, red, ovoid stone between its eyes that gives off a faint glow.

Large monstrosity, unaligned

Armor Class 18 (natural armor)
Hit Points 210 (20d10 + 100)
Speed 40 ft., swim 40 ft.

22 (+6) 16 (+3) 20 (+5) 4 (-3) 14 (+2) 16 (+3)

Saving Throws Dexterity +7, Wisdom +6
Skills Perception +6, Stealth +7
Damage Resistances fire
Damage Immunities necrotic, poison
Condition Immunities poisoned
Senses darkvision 60 ft., passive Perception 16
Challenge 12 (8,400 XP)

Special Traits

  • Amphibious. The horned serpent can breathe air and water.
  • Corpse Cough. Those who fail a saving throw against the horned serpent’s Gem Gaze or bite attack become infected with the corpse cough disease. The infected creature can’t benefit from short or long rests due to a constant, wet cough. The infected creature must succeed on a DC 17 Constitution saving throw each day or take 18 (4d8) necrotic damage. The target’s hp maximum is reduced by an amount equal to the necrotic damage taken. The target dies if this effect reduces its hp maximum to 0. The reduction lasts until the target is cured of the disease with a greater restoration spell or similar magic. If the infected creature comes into physical contact with a blood relative before the disease is cured, the relative must succeed on a DC 17 Constitution saving throw or also become infected with the disease. The blood relative is afflicted with a constant, wet cough within hours of infection, but the disease’s full effects don’t manifest until 1d4 days later. Corpse cough is so named due to the smell of the cough as the infected creature’s lungs become necrotic.
  • Poisonous Aura. At the start of each of the horned serpent’s turns, each creature within 20 feet of it must make a DC 17 Constitution saving throw, taking 18 (4d8) poison damage on a failed save, or half as much damage on a successful one.
  • Shielded Mind. The horned serpent is immune to scrying and to any effect that would sense its emotions, read its thoughts, or detect its location.


  • Multiattack. The horned serpent makes one gore attack and one bite attack.
  • Gore. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 19 (4d6 + 5) piercing damage.
  • Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 21 (3d10 + 5) piercing damage, and the target must succeed on a DC 17 Constitution saving throw or become infected with the corpse cough disease (see the Corpse Cough trait).
  • Gem Gaze (Recharge 5–6). The horned serpent’s gem flashes, bathing a 30-foot cone in iridescent light. Each creature in the area must make a DC 17 Constitution saving throw. On a failed save, a creature takes 35 (10d6) radiant damage and is infected with the corpse cough disease (see the Corpse Cough trait). On a success, a creature takes half the damage and isn’t infected with the disease. Gem Gaze has no effect on constructs and undead.


Plague Bearers. Known to be a bringer of magical plagues, horned serpents are also sought after for their horns and the strange stones between their eyes, both believed to have powerful curative properties.

Wilderness Wanderer. Horned serpents travel between lakes, ponds, and deep rivers, never staying in one area for more than a few seasons. Though they live primarily in the water, they venture onto the land to hunt, where the sweetness of their poisonous scent draws game to them.

Grisly Signs. The presence of a horned serpent is most often detected by an area of dead creatures, poisoned but otherwise untouched.

Section 15: Copyright Notice

Creature Codex. © 2018 Open Design LLC; Authors Wolfgang Baur, Dan Dillon, Richard Green, James Haeck, Chris Harris, Jeremy Hochhalter, James Introcaso, Chris Lockey, Shawn Merwin, and Jon Sawatsky.