Curse of the Crimson Throne
Most native Korvosans have heard stories about the wererats, otyughs, and goblins said to haunt the deeper Vaults under the city, but few have heard of the pervasive derro. These small, three-fingered, blue-skinned menaces operate in semiindependent groups beneath several regions of the city.
Derro are sometimes responsible for mysterious disappearances (to say nothing of confused reappearances), as well as cattle and pet mutilations. When those kidnapped
by derro suddenly and inexplicably return to Korvosa, they frequently have only vague and horrifying memories of the missing time. They speak of bizarre experiments, painful tortures, and an ever-present pale blue light.