Deep-Earth Humanoid • Poisoner • Subterranean Raider
Derro
Derro are small, pale subterranean humanoids known for poison, ambush, abduction and strange illusion and sonic magic.
Derro
Derro are intelligent, tool-using inhabitants of the deep places beneath the surface world. Most stand close to three feet tall. Their skin is chalk-white, pale grey or faintly blue-violet, their hair is usually white or ash-grey, and their disproportionately large, milky-white eyes are adapted to life in near-total darkness.
They manufacture weapons, preserve food, prepare poisons, set traps and maintain hidden settlements beneath mines, buried cities, ruins and natural cavern systems. Their magic commonly manipulates darkness, misleading sound, disorientation and sudden concussive noise.
Their favoured weapons include short swords, repeating light crossbows and the aklys, a hooked throwing club fitted with a retrieval cord.
Derro are infamous for raids against surface communities. They seek food, medicine, tools, unusual substances, written knowledge and living captives. Prisoners may be questioned, observed, experimented upon, enslaved or exchanged. A few eventually return to the surface with incomplete or contradictory memories of what happened below.
Derro are not mindless creatures. Their civilisation depends upon language, craft, planning, poison-making, sorcery and organised raiding. The Intelligence 1 interpretation formerly carried on this page is not used in SpiralWorlds.
Game Statistics
Derro
Small Humanoid (Derro), typically Chaotic Evil
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 10 (+0) Save +0 |
16 (+3) Save +5 |
12 (+1) Save +1 |
11 (+0) Save +0 |
8 (−1) Save −1 |
14 (+2) Save +4 |
Traits
Fractured Mind. The derro has Advantage on saving throws against being Charmed and against effects that magically alter its thoughts, emotions or perceptions.
Magic Resistance. The derro has Advantage on saving throws against spells and other magical effects.
Sneak Attack (1/Turn). The derro deals an extra 3 (1d6) damage when it hits a creature with a weapon attack while it has Advantage on the attack roll, or when an ally of the derro is within 5 feet of the target and the derro does not have Disadvantage on the attack roll.
Sunlight Vulnerability. While in sunlight, the derro has Disadvantage on attack rolls and ability checks. At the end of each continuous hour it spends in sunlight, the derro gains 1 level of Exhaustion. One level of Exhaustion gained in this way is removed after each 24-hour period the derro spends underground or otherwise completely sheltered from sunlight.
Deep-Earth Sorcery. The derro can create a minor sensory illusion at will. Once per day it can cast Darkness without requiring a Material component. Charisma is its spellcasting ability (spell save DC 12).
Actions
Multiattack. The derro makes two attacks using its Aklys, Short Sword or Repeating Light Crossbow in any combination.
Aklys. Melee or Ranged Attack Roll: +5, reach 5 ft. or range 20/60 ft. Hit: 6 (1d6 + 3) Bludgeoning damage. Once per turn, a Large or smaller creature hit by the aklys must succeed on a DC 13 Strength saving throw or have the Prone condition.
Short Sword. Melee Attack Roll: +5, reach 5 ft. Hit: 6 (1d6 + 3) Piercing damage.
Repeating Light Crossbow. Ranged Attack Roll: +5, range 80/320 ft. Hit: 6 (1d6 + 3) Piercing damage. Once per turn, a creature hit by a poisoned bolt must succeed on a DC 12 Constitution saving throw or take an additional 3 (1d6) Poison damage.
Sonic Burst (1/Day). The derro releases a magical concussion at a point it can perceive within 60 feet. Each creature within 10 feet of that point must make a DC 12 Constitution saving throw, taking 9 (2d8) Thunder damage on a failed save or half as much damage on a successful one. A creature that fails the save has the Deafened condition until the end of its next turn.
Derro CR 3
XP 800 • CE Small humanoid (derro)
Defense
Offense
Statistics
Special Abilities
Madness (Ex). A derro uses its Charisma modifier instead of its Wisdom modifier on Will saves and is immune to insanity and confusion effects. A miracle or wish can remove this supernatural condition; doing so increases Wisdom by 6 and reduces Charisma by 6.
Poison Use (Ex). Derro can safely handle poison without accidentally poisoning themselves. A typical derro carries 10 crossbow bolts coated with Medium spider venom: injury; Fortitude DC 14; frequency 1/round for 4 rounds; effect 1d2 Strength damage; cure 1 save.
Vulnerability to Sunlight (Ex). A derro takes 1 point of Constitution damage for every hour it remains exposed to sunlight.
Ecology
Derro
Small Monstrous Humanoid • Usually Chaotic Evil • CR 3
| Hit Dice | 3d8+3 (16 hp) |
|---|---|
| Initiative | +6 |
| Speed | 20 ft. |
| Armor Class | 19 (+1 size, +2 Dex, +2 natural, +3 studded leather, +1 buckler), touch 13, flat-footed 17 |
| Base Attack/Grapple | +3/−1 |
| Attack | short sword +4 melee (1d4/19–20) or repeating light crossbow +6 ranged (1d6/19–20 plus poison) |
| Full Attack | short sword +4 melee (1d4/19–20) or repeating light crossbow +6 ranged (1d6/19–20 plus poison) |
| Space/Reach | 5 ft./5 ft. |
| Special Attacks | poison use, spell-like abilities, sneak attack +1d6 |
| Special Qualities | madness, darkvision 60 ft., spell resistance 15, vulnerability to sunlight |
| Saves | Fort +2, Ref +5, Will +6 |
| Abilities | Str 11, Dex 14, Con 13, Int 10, Wis 5, Cha 16 |
| Skills | Bluff +5, Hide +10, Listen +1, Move Silently +8 |
| Feats | Blind-Fight, Improved Initiative |
| Environment | Underground |
| Organization | team (2–4), squad (5–8 plus 1 3rd-level sorcerer), or band (11–20 plus 30% noncombatants plus 3 3rd-level sorcerers and 1 5th–8th-level sorcerer) |
| Treasure | Standard coins; double goods; standard items |
| Advancement | By character class |
| Level Adjustment | — (+2 if sane) |
Special Abilities
Madness (Ex). A derro uses its Charisma modifier instead of its Wisdom modifier on Will saves and is immune to confusion and insanity effects. A miracle or wish can remove the condition, increasing Wisdom by 6 and reducing Charisma by 6.
Poison Use (Ex). Derro safely handle their own poisons and commonly coat crossbow bolts with greenblood oil or monstrous-spider venom.
Sneak Attack (Ex). A derro deals +1d6 damage when attacking a foe denied its Dexterity bonus to AC or while flanking, subject to the normal limitations of sneak attack.
Spell-Like Abilities. At will— darkness, ghost sound; 1/day— daze (DC 13), sound burst (DC 15). Caster level 3rd; save DCs are Charisma-based.
Vulnerability to Sunlight (Ex). A derro takes 1 point of Constitution damage for each hour of sunlight exposure. If its Constitution reaches 0 from this damage, it dies. One point lost in this way returns for each 24-hour period the derro spends underground or otherwise completely sheltered from sunlight.
Skills. Derro receive a +4 racial bonus on Hide and Move Silently checks.
Origins and Ancestry
No surviving account proves where the first derro came from. Surface natural philosophers, underground peoples and derro communities themselves preserve several incompatible explanations. SpiralWorlds treats these as competing traditions rather than declaring any one of them absolute.
The Dwarven Theory
Some scholars connect derro with the wider family of subterranean peoples that includes dwarves. Their underground adaptation and strong craft traditions are suggestive but do not prove common ancestry.
The Fey Theory
Another widespread explanation claims that the oldest derro descend from subterranean fey altered by countless generations beneath the Earth.
The Created-People Theory
Some fragmentary Deep-Earth traditions suggest that derro ancestors were deliberately changed by an older underground civilisation and used as workers, servants, soldiers or experimental subjects.
Deep-Earth Frontier
Derro inhabit mines, cavern systems, buried ruins and deeper networks that may eventually connect with approaches to the Hollow Earth. They are not the Dero of the Hollow Earth, a separate subterranean people associated with ancient machinery and a different ancestry. The two peoples may encounter one another where their territories overlap, but their names are not interchangeable.
Appearance
A typical derro is compact and strongly built for its height, with broad shoulders, long fingers and a low centre of gravity. Four-fingered hands occur in many old descriptions. Skin pigmentation is minimal, ranging from dead white through pale slate to bluish grey.
The eyes are their most striking feature: large, round and usually solid white or milk-pale, without an obvious visible pupil. Underground those eyes give the derro exceptional vision. Under the sun, the same adaptation becomes dangerous.
Derro clothing is practical and often scavenged. Leather, cured cave-hide, stolen cloth, crossbow cases, hooked weapons, tool harnesses and belts of poison vials are common. Wealthier individuals decorate equipment with polished bone, crystal fragments, unfamiliar metals or trophies recovered from deeper ruins.
Society
There is no universal derro empire. Their civilisation consists of scattered enclaves, warrens, fortified caverns, occupied mines and buried settlements separated by dangerous underground territory. Two neighbouring communities may share a language while maintaining generations of mutual hostility.
Authority commonly belongs to whoever controls something essential: water, food, access to the surface, poisons, prisoners, secret routes or magical knowledge. Derro sorcerers often become prophets, rulers, interrogators or custodians of hidden lore, while rogues serve as scouts, kidnappers and tunnel-raiders.
Their supernatural cognitive alteration does not make them incapable of planning. A derro community may keep meticulous inventories, maintain sophisticated traps and organise patrols while simultaneously accepting beliefs that outsiders find bizarre, obsessive or internally contradictory.
Legacy rules terminology: PF1e and D&D 3.5e statistics use the special ability name Madness. SpiralWorlds retains that historical mechanical term while treating the condition as a specific supernatural alteration of derro cognition rather than a statement about real-world mental illness.
Habitat and Ecology
Derro favour deep limestone systems, abandoned mines, volcanic galleries, collapsed foundations, buried settlements, subterranean aquifers and ancient artificial passages. They require places where prolonged exposure to sunlight is impossible.
They are omnivorous and opportunistic. Fungal gardens, blind fish, cave insects, roots, preserved meat, captured livestock and stolen surface provisions all appear in derro settlements. Larger enclaves maintain cisterns, mushroom beds, workshops and storage caverns.
Derro depend heavily upon salvage and raiding. Timber, worked iron, cloth, glass, medicines, alchemical ingredients, books and lamps are valuable because many are easier to steal from surface communities than manufacture deep underground.
Not every cave or mine contains derro. Their communities require water, food, defensible terrain and routes suitable for concealed movement. Human excavation becomes dangerous when miners, quarrymen or builders unknowingly break into tunnels that were never truly abandoned.
Surface Raids and Abductions
Derro prefer controlled incursions to open warfare. Scouts locate an isolated entrance, study local routines and prepare secondary escape passages before the main group moves.
They favour lone workers, sleeping households, prisoners, travellers, night watchmen and people living close to old cellars or underground works. Poisoned bolts, darkness and misleading sounds isolate victims before raiders close in.
A derro raid rarely aims at conquest. Its purpose is acquisition: captives, medicines, tools, books, metal, specimens or information. Once the objective is secured, the raiders withdraw rapidly into passages too cramped or confusing for most surface pursuers.
Derro in 1454
In 1454, most surface communities do not know that derro exist. They know disappearances, poisoned bolts, tapping behind mine walls and tales of pale figures glimpsed where no human settlement should be.
Miners are among the most common witnesses. A shaft begins producing unfamiliar knocking from beyond a wall. Tools vanish from a locked gallery. A worker disappears. Days later another miner finds an unknown passage cut through stone behind a collapsed seam.
In ancient towns, derro may exploit forgotten drains, buried foundations, old quarries, catacombs or earlier subterranean works to approach the surface without entering open streets. The best-hidden enclaves may remain undiscovered for generations.
Surface explanations vary. Missing people are blamed on robbers, mine spirits, rival guilds, wolves, witchcraft or ordinary murder. Experienced underground peoples, occult scholars and survivors of previous incursions are more likely to recognise the pattern.
Signs of Derro Activity
- Small crossbow bolts coated in carefully prepared venom.
- Knocking or whistling from passages believed to be sealed.
- Small booted footprints in inaccessible underground galleries.
- Hook marks in wood or stone left by an aklys or similar tool.
- Missing lamps, glassware, medicines, books or metal tools.
- Victims who remember lights, voices or machinery only in disconnected fragments.
- New tunnels entering cellars, mines, drains or catacombs from below.
Combat and Tactics
Derro prefer an ambush to a stand-up fight. They scout the battlefield, establish escape routes, prepare poison and attack where darkness, confined terrain and confusing sound favour them. Their objective is frequently to isolate and capture one creature rather than kill every opponent.
Ambush
Derro open from concealment with poisoned crossbow fire, deceptive noises and magical darkness.
Control
Aklyses, narrow passages, traps and sudden sonic effects disrupt pursuit and separate companions.
Capture
An incapacitated or isolated opponent is dragged toward a prepared tunnel rather than left on the battlefield.
Retreat
Derro abandon expendable positions rather than fight to extinction, withdrawing through shafts and passages prepared in advance.
Using Derro in a Campaign
Derro are strongest when the first encounter is with evidence rather than the creature itself. A poisoned bolt, a newly opened tunnel or a survivor with incomplete memories can establish a subterranean mystery long before combat begins.
The Mine That Answers
Miners hear tapping from beyond a supposedly solid wall. Each night the answering rhythm comes closer, although no new excavation can be found.
The Returned Captive
A missing traveller reappears miles from home bearing unfamiliar scars, a stolen derro token and no coherent memory of the previous nine nights.
The Cellar War
Several neighbouring houses discover narrow tunnels entering their foundations. All of the passages converge on an older structure buried beneath the town.
The Broken Enclave
A derro settlement has been abandoned in haste. The question is not where its inhabitants went, but what entered their caverns and drove them toward the surface.
Further Viewing
This longer dedicated Derro lore discussion is retained because it provides substantially more useful background than short-form monster summaries.
Rules Sources and Provenance
SpiralWorlds: The setting material, Deep-Earth treatment, 1454 integration and 5.5e conversion on this page are presented for SpiralWorlds campaigns.
Derro and Dero: The Derro described on this page are distinct from the technologically associated Dero already present in SpiralWorlds Hollow Earth material. Similarity of name does not indicate that the two peoples are identical.
Pathfinder 1e: The PF1e Derro statistics derive from the Pathfinder Roleplaying Game treatment of the creature. External rules reference .
D&D 3.5e: The legacy 3.5e statistics derive from the Open Game Content Derro in the 3.5 System Reference Document. External SRD reference .
Section 15 Copyright Notice
System Reference Document. Copyright 2000, Wizards of the Coast, Inc.; Authors Jonathan Tweet, Monte Cook and Skip Williams, based on original material by E. Gary Gygax and Dave Arneson.
Pathfinder Roleplaying Game Bestiary. Copyright 2009, Paizo Publishing, LLC; Author Jason Bulmahn, based on material by Jonathan Tweet, Monte Cook and Skip Williams.