Derro are the degenerate offspring of humans and dwarves, created by some malign deity in ages past. They resemble small dwarves but have grey or blue skin and white hair. Unlike true dwarves, very few derro have beards. Derro are naturally insane, either because of their unusual mixed heritage or because of some cruel choice by their creator. They often possess multiple mental disorders, with schizophrenia and multiple personalities being the most common. In fact, nearly one in ten derro are so horribly psychotic that they do not survive past their first year of life.