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Ferrous Worm

Medium monstrosity, unaligned

Armor Class 16 (natural armor)
Hit Points 27 (5d8 + 2)
Speed 30 ft., burrow 30 ft.

13 (+1) 17 (+3) 12 (+1) 12 (+1) 13 (+1) 5 (-3)

Saving Throws Constitution +3
Skills Perception +3, Stealth +7
Condition Immunities prone
Senses darkvision 60 ft., tremorsense 60 ft., passive Perception 14
Challenge 3 (700 XP)

Special Traits

  • Earth Glide. The ferrous worm can burrow through nonmagical, unworked earth and stone. While doing so, the ferrous worm doesn’t disturb the material it moves through.
  • Camouflage. The ferrous worm has advantage on Dexterity (Stealth) checks made to Hide in rocky terrain and treasure piles.
  • Treasure Sense. The ferrous worm can pinpoint, by scent, the location of precious metals and stones, such as coins and gems, within 60 feet of it.


  • Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 10 (2d6 + 3) piercing damage, and the target must succeed on a DC 13 Constitution saving throw or be poisoned and take an additional 10 (3d6) poison damage each day until cured. The poison can only be cured by casting lesser restoration.


These semi-intelligent subterranean creatures are found almost exclusively in treasure hoards where masses of metallic coins are present.

Originally from the Quasi-Elemental Plane of Minerals, ferrous worms require close contact with metallic objects in order to maintain their bodily functions, much like fish require water. In their homeworld, such contact is omnipresent, but when brought to the Prime Material Plane to serve their summoner’s needs, ferrous worms depend on alternate sources of metal for survival. They burrow deeply into large accumulations of treasure, attacking anyone who disturbs their surrogate home.

Ferrous worms use the element of surprise to their tactical advantage, often clamping their metal teeth on several victims before their unsuspecting targets can react. Not only is the creature’s bite quite destructive as its metal teeth are ground to fine points, but any humanoid bitten by a ferrous worm must make a saving throw or contract a blood disease. This disease is the result of a sudden injection of heavy minerals into the system, including lead, mercury, beryllium, and lithium. Over the next 1d4 days, victims experience abdominal pains, headaches, and short-term memory problems. After another 1d4 days, their condition worsens, resulting in seizures and a loss of 3d6 hit points per day until death. Though the hit point loss may be abated with curative magic, only a successful cure disease restores the victim to full health.

Ferrous worms are solitary creatures except during the brief mating season when they burrow long distances through mineral-rich earth to locate a mate. The mating ritual requires several days to compete; if encountered at this time, ferrous worms are non-hostile unless openly attacked.

Section 15: Copyright Notice

Tome of Horrors © 2018, Frog God Games, LLC; Authors: Kevin Baase, Erica Balsley, John “Pexx” Barnhouse, Christopher Bishop, Casey Christofferson, Jim Collura, Andrea Costantini, Jayson ‘Rocky’ Gardner, Zach Glazar, Meghan Greene, Scott Greene, Lance Hawvermale, Travis Hawvermale, Ian S. Johnston, Bill Kenower, Patrick Lawinger, Rhiannon Louve, Ian McGarty, Edwin Nagy, James Patterson, Nathan Paul, Patrick N. Pilgrim, Clark Peterson, Anthony Pryor, Greg Ragland, Robert Schwalb, G. Scott Swift, Greg A. Vaughan, and Bill Webb