Mind flayers must be stopped. They have visited horrors on countless worlds, and entire groups of people have been mutated by illithid experiments. Such are the derro.

Whenever I've met them, I refuse to fight, no matter how violent they might be. I think of the dwarves they once were. and I must confess that even I have shed tears.

Derro slink through the subterranean realms, seeking places that are safe from the perils of the Underdark. Equal parts fearful and vicious, bands of these dwarf-kin prey on those weaker than themselves, while giving simpering obeisance to any creatures they deem more powerful. A lone derro may seem pitiable, but a cackling, spitting, growling, howling horde of them is horrifying to behold.

Fractious in groups and individually weak, derro would have died out long ago but for two elements of their character. They are cautious and distrustful, which serves them well as they navigate the dangers of the Underdark and its societies. They also have a stronger-than-normal tendency to develop sorcerous power. Individuals who do so usually serve as leaders and are known as savants.

Grandiose fantasies and rampant fanaticism have obscured derro's true origin, even among themselves. Most dwarves don't recognize derro as kin, but the legends that derro tell about their people and the story that duergar believe share a grain of truth. According to the histories of some duergar, derro are descended from a dwarven community that was left behind when the others escaped the rule of mind flayers. These remnants were so distorted by the mind flayers' psionic power that the dwarves became Aberrations.

Derro tell their own stories of flight and survival in the Underdark, in which mind flayers aren't always the enemy. They tell of two brothers, the gods Diirinka and Diinkarazan, and of how Diirinka cleverly betrayed his sibling so that he could steal magical power from the evil they escaped. The danger the brothers are said to face in this legend varies, depending on whatever foe the savants want to lead their people against, yet the essence of the story remains the same: a lesson of survival at any price and an example of how deceitfulness and cruelty can be virtues.

Mad as hatters, every one of them. No derro has ever been sane, but neither is every form of madness a hindrance.

Derro

Derro slink through the subterranean realms, seeking places that are safe from the perils of the Underdark. Equal parts fearful and vicious, bands of these dwarfkin prey on those weaker than themselves, while giving simpering obeisance to any creatures they deem more powerful. Wild-haired, haggard, shuddering, and shabbily dressed, a lone derro seems a pitiable creature, but when a cackling, spitting, growling, howling horde of them attacks, the sight inspires both fear and revulsion.

Madness and Sorcery

Fractious in groups and individually weak, derro would have been driven to extinction long ago but for two elements of their character. They have an inborn tendency toward paranoia, a peculiarity that serves them well as they navigate the dangers of the Underdark and its societies. They also have a stronger-than-normal tendency to develop sorcerous power. Individuals who do so become their leaders, known as savants. The derro consider these sorcerers to be specially blessed by their deity, Diirinka.

Forgotten Duergar

Grandiose fantasies and rampant fanaticism have obscured the true origin of the derro, even among themselves. Most dwarves don't recognize derro as kin, but the legends that the derro tell about their race and the story that the duergar believe share a grain of truth.

According to the duergar, the derro are descended from dwarves of a clan that was left behind when the others escaped the mind flayers' rule. They eventually also got away, but not before becoming demented and contorted.

The derro tell their own story of flight and survival in the Underdark, and the mind flayers aren't always the enemy. Laduguer and Deep Duerra don't feature in their mythic history. Instead they tell of two brothers, Diirinka and Diinkarazan, and of how Diirinka cleverly betrayed his sibling so that he could steal magical power from the evil they escaped. The danger the brothers are said to face in this legend varies, depending on whatever foe the savants want to lead their people against, yet the essence of the story remains the same: a lesson of survival at any price and an example of how deceitfulness and cruelty can be virtues.

Derro Madness

All derro suffer from a form of madness that most often manifests as mania and paranoia, but other mental afflictions and strange tics also commonly affect them. Derro take little notice of odd behavior in their ranks, except when an individual displays the characteristics of a savant. They believe the strange behavior of savants arises because those leaders carry messages from Diirinka. You can use the Derro Madness|MTF table to generate one or more odd qualities for a derro NPC.

The derro are degenerate Underdark humanoids that resemble small dwarves. Cruel and insane, they take delight in tormenting others—even their own kind.

Derro have blue-gray skin and straight hair that is white or yellow in color. Their uniformly pale white eyes lack both irises and pupils.

Unnatural Origin

Derro believe they were created by their god, Diirinka, but they are actually the result of cruel experiments on dwarves by mind flayers. Like duergar, the derro were a slave race to the mind flayers, but eventually freed themselves.

Born to Madness

The process of their creation rendered the derro irrevocably insane. They cooperate with each other only out of necessity and when riled up by a charismatic leader.

Life of Attrition

Derro can live to be one hundred and fifty years old, but they mature and breed quickly. When their elders deem that their numbers are becoming unmanageable, the derro declare war on some other race and surge forth in a reckless horde, fighting until their population dwindles to a tolerable size. These ghastly purges weed out the weak among the derro and are referred to as "Uniting Wars."

Second-Class Citizens

Derro create no settlements of their own. Instead, they form small, isolated enclaves in non-derro settlements throughout the Underdark, where they are treated as vermin or slaves. Their own cutthroat politics prevent the derro from mounting any effective resistance against such exploitation.

Derro Weapons

The derro wield special weapons. They use a hooked shortspear, which is a martial melee weapon that deals 1d4 piercing damage, weighs 2 pounds, and has the light weapon property (see chapter 5, "Equipment," of the Player's Handbook). It doesn't possess the thrown or versatile weapon properties of a normal spear. On a hit with this weapon, the wielder can forgo dealing damage and attempt to trip the target, in which case the target must succeed on a Strength saving throw or fall prone. The DC is 8 + the wielder's Strength modifier + the wielder's proficiency bonus.

The derro also use a light repeating crossbow|OotA fitted with a cartridge that can hold up to six crossbow bolts. This weapon is similar to a light crossbow except that it has half the range (40/160 feet) and doesn't have the loading property. It automatically reloads after firing until it runs out of ammunition. Reloading the cartridge takes an action.

Derro who have just begun to discover and control their magic are called apprentices. The magic of a derro apprentice is dangerous and unpredictable.

Derro

Derro are Underdark dwellers of dubious origin. According to the histories of some duergar, derro are descended from a community of dwarves that was left behind when the others escaped the rule of mind flayers. The mind flayers' psionic power eventually transformed these forsaken dwarves into Aberrations.

You can learn more about derro in Mordenkainen Presents: Monsters of the Multiverse.

Hostility and greed are guiding values for some derro. These derro indiscriminately raid settlements and rob travelers regardless of the apparent value of any goods they steal. These derro believe such acts are sanctioned by their despicable god, Diirinka, who delights in cruelty and destruction.

Derro are Underdark dwellers of dubious origin. According to the histories of some duergar, derro are descended from a community of dwarves that was left behind when the others escaped the rule of mind flayers. The mind flayers' psionic power eventually transformed these forsaken dwarves into Aberrations.

You can learn more about derro in Mordenkainen Presents: Monsters of the Multiverse.