Derro (Dungeons & Dragons)

The derro are a fictional species in the Dungeons & Dragons fantasy role-playing game. They were first devised for the Advanced Dungeons & Dragons First Edition Monster Manual. Derro are also a race of humanoids that dwell in the Underdark. Derro are widespread and are likely to be found in small bands throughout the Underdark. Derro warrens exist in many drow and duergar cities, and independent derro strongholds lie in the deepest reaches of the Realms Below. Derro scouts and marauders search the areas near and around their settlements for victims to enslave and torment.

The derro are a strange and sadistic race; furthermore, they are clever, stealthy, and murderously insane. It is very common for a derro to devote his or her self to some strange quest, such as collecting only certain types of gemstones for a magical device or slaying as many members of a particular race as possible. Other derro are assigned specific missions by powerful derro savants. These mission-driven derro might join a company of comrades to fulfill their irrational goals.

The origins of the derro are unknown. One legend states, however, that the derro are a result of genetic breeding performed by mind-flayers on members of an entire dwarven clan; in the Forgotten Realms setting, this clan is named as the clan of Delzoun.

Possible Creative Origins
It is possible that derro were derived from Richard Sharpe Shaver's Deros.

Forgotten Realms creatures