Derro are a degenerate race of dwarven stature. They have dwelled in the Underdark for ages, but they were discovered by the mind flayers only five centuries ago, and by the drow but shortly before that. The derro have made a name for themselves by their marked cruelty. It is said that a derro lives for two things: the slow and humiliating death of surface demihumans and especially humans, and the perversion of knowledge for their own dark ends.

Derro are short, with skin the color of an ice-covered lake (white, with bluish undertones), sickly pale yellow or tan hair (always straight), and staring, pupil-less eyes. Their features remind dwarves of humans, and vice versa. Derro have rough skin, spotted with short coarse tufts of hair. Most derro wear a loose costume woven from the hair of underground creatures and dyed in deep reds and browns. Even in full armor, exploring new territory or patrolling their own, derro are easily recognizable. Their armor is leather, studded in copper and brass. Leaders, though, wear tougher leather armors, made from the hides of creatures far tougher than cattle. Derro prefer weapons designed to cripple opponents, rather than those built for a quick kill: derro don’t see any sport in spears and axes.

Combat: Derro are one of the most dexterous of humanoid races (averaging 15-18) and their Armor Class must be adjusted for this. Normally, a derro party is well-equipped with weapons and spells. All derro carry small, ornamental blades, called secari, which can be treated as daggers, but most use other weapons as well.

Half of encountered derro carry a repeating light crossbow (12 maximum range, two shots each round, six-bolt capacity, 1d3 points of damage). Virtually every derro crossbowman coats his bolts with poison. If a derro wants to simply bring down his prey, he uses a poison that causes an additional 2d6 points of damage (successful saving throw for no additional damage). If a derro wishes to prolong his target’s suffering, he uses a poison that has the same effects as the ray of enfeeblement spell (again, a successful saving throw indicates no poison damage).

Twenty-five percent of derro carry a hook-fauchard, a long (6’+) pole arm that causes 1d4 points of impaling damage and can pull a man-sized or smaller creature off-balance 25% of the time. An off-balance character must spend the next round regaining his balance.

Fifteen percent of derro use only a spiked buckler (a small shield, improving the creature’s AC by 1 against any one opponent, armed with a central spike, which can be wielded as a second weapon with no penalty [because of the derro’s high Dexterity] for 1d4 points of impaling damage) and a hooked aklys. The aklys is a short, heavy club that can be thrown for 1d6 points of crushing damage. It is attached to a thick, leather thong so that it might be retrieved. Thanks to the hook, the aklys also pulls an opponent off-balance, as the hook-fauchard above, though it has only a one-in-eight chance. These derro are considered brave by their fellows: they are awarded the rarer, heavier armors (AC 4).

The remaining 10% of derro encountered are the sons and daughters of derro leaders. They are given heavier armor as well,and are trained in the use of spear and military pick. They alsouse bucklers (without spikes) when they are not using the spear two-handed.For every three derro encountered, there is one additional derro with 4 Hit Dice. For every six derro, there is one with 5 Hit Dice. If ten or more are encountered, there is always an additional 7-Hit Die leader with a 6-Hit Die lieutenant. (So if a party encountered 25 derro, these would be accompanied by eight 4-Hit Die derro, four 5-Hit Die derro, one derro with 6 Hit Dice, and one with 7.) These leader types always wear the thicker armor and usually wield well-made (occasionally magical) weapons.

If 20 or more derro are encountered, they are accompanied by a savant and two student savants. Savant derro are sage-like, able to use any sort of magical item and weapon. Savants know 1d4+5 of the following spells, learned at random: affect normal fires, anti-magic shell, blink, cloudkill, ESP, hypnotic pattern, ice storm, invisibility, levitate, light, lightning bolt, minor creation, paralyzation, repulsion, shadow magic, spider climb, ventriloquism, wall of fog, wall of force. Savants have 5-8 Hit Dice, and carry two or three useful magical items. Typical magical items are any potion, any scroll, rings of fire resistance, invisibility, protection, and spell storing, any wand, studded leather armor +1, shields, weapons up to +3, bracers of defense, brooches of shielding, cloaks of protection, and so on. Savants can instinctively comprehend languages and read magic (as the spells).

Savants are also capable of acting as sages in one to three areas of study. Derro raiding parties’ missions are often inspired by a savant’s research.

Student savants know only 1-3 spells, have 4-7 Hit Dice, know only one field of study, and typically have one minor magical item. They are otherwise identical to their savant teachers.

In combat, derro fight with cunning and good tactics. Their goals are to separate an enemy from his weapons (perhaps by snagging a weapon with a hook-fauchard [on an attack roll to hit AC 6] and then pressing the battle, keeping the unfortunate opponent away from his dropped weapon), keep spellcasters from effectively using magic, and inflict minor wounds until they eventually kill their opponents. Savants use their powers to confuse and frustrate, rather than to simply kill. For instance, a lightning bolt spell would be used to seal off an escape route, but well ahead of the party of humans fleeing down it. Derro have poor infravision (30-foot range) but keen hearing (treat as the blind-fighting nonweapon proficiency).

Derro keep slaves and attempt to capture intelligent opponents, if possible.

Habitat/Society: Derro dwell in large underground complexes, nearer the surface than the kuo-toa and drow, but deeper than goblins and trolls. They never expose themselves to direct sunlight, as it nauseates them. Sunlight would kill a derro were he to be exposed to it for a few days. Yet derro occasionally visit the surface world at night, raiding for humans or carrying out a savant’s plans.

Derro are never encountered singly. From their combat tactics to their choice of spells, derro demonstrate a mob mentality. A lone demo (the last survivor of an ill-fated patrol, perhaps) is a desperate derro, seeking at all costs to return to his home lair.

A derro lair always has 3d4 + 30 normal derro, plus leaders. The members of the lair are led by the resident savants (1-3 in number) and their apprentices (2-5 student savants). Derro unquestioningly obey the puzzling, even suicidal, dictates from their savant leaders.

Should a lair grow very much over 40 inhabitants, half the group (with half the savants and half the leaders) will split off and form an independent community. Such a splinter group will travel quite a distance before settling down, as no two derro lairs have been spotted within several miles of each other. The two groups may communicate for a short time, in order to ensure the new lair’s safety, but they soon sever all contacts and act utterly independently of one another. Although it is possible for two lairs to be at war with one another, or to join in combat against a common enemy, no examples of these behaviors have ever been recorded, with the exception of the regular Uniting War, described below.

Also to be found in a derro lair are 5d6+10 human slaves. If any of the lair’s savants or students know the charm person spell, each slave has a 90% chance of being charmed. Derro hate humans more than any other race; they use humans for the most demeaning manual labor and for breeding.

The derro are said to have a major stronghold somewhere in the Underdark, and there the savants plot and scheme to devastate the surface world and enslave all humanity.

Derro do not appear to worship any powers, but the savants treasure knowledge and the rest of the race pretty much worships the savants. The worst criminals in the derro community, subject to the Polite Execution (which takes a good two weeks, and which roams over miles of subterranean territory), are those who do not follow the laws of the savants.

Most of those laws have to do with the derros’ goals: the destruction of humanity and the acquisition of arcane and obscure information. Derro usually scour their territory for magical items, stealing them or, if necessary, purchasing them from more powerful creatures. Derro do not share the love of gold common to their dwarfish relatives, and they have been known to pay exorbitant prices for a few potions or for a magical item with a missing command word.

This serves as one of the bases of trade between derro and other races of the Underdark. Drow find derro to be dangerous opponents (due to the latter’s magic resistance) and a race of barbarians with too much interest in the surface world. The mind flayers think the derro taste bad. Duergar disapprove of the derro’s love of cruelty. And derro really don’t much care about the other races deep beneath the surface. But derro often raid the surface and acquire technology or items that other deep races desire, and so limited trade between a lair and some surrounding creatures is possible.

Every 20 years or so, the derro race mounts an all-out war against other creatures of the Underdark. This is known as the Uniting War, and no savant really expects to win it. The War is a means of winnowing out the weakest of the derro lairs, a focal point for racial identity, and a chance to really start some terror throughout the Underdark. It also serves the purpose of starting rumors. That is, humans will certainly hear that a war is being fought in the Underdark, and will send hundreds of scouting and adventuring parties into the deep underground to investigate. The derro welcome this new source of slaves.

Ecology: Derro can live on a diet of underground fungi, but they find the stuff to be foul-tasting if used as anything other than spices. Thus they seek out other sustenance whenever possible. A derro hunting party usually pursues large, dangerous prey that can feed the entire lair, rather than smaller, simpler food. The derro tendency to torment prey holds true with hunting for food.

The derro also raid other races for food. Sometimes, they merely rob the dwarves or the orcs, hoping to provoke an amusing conflict. But such excursions are tame compared to Open Hunting, the derro term for midnight raids into human settlements. When Open Hunting, a derro party steals cattle and swine, to let loose and hunt at a later time, but it primarily kidnaps humans. As mentioned before, derro treasure humans for slaves and for breeding.

Derro have few other roles in the underground ecosystem. In the last few Uniting Wars, the drow noticed that derro blood (a milky substance that turns brown and rotten upon the slightest exposure to bright light) was a useful ingredient in drow potions.