The majority of children born in the various calla were twins, and as such their brains possessed a specific property crucial to the ability of the Breakers in Blue Heaven for breaking the Beams, which can be used to supported the Dark Tower. The process of extracting this necessary brain matter from one of a pair of twins would leave the child in a state of extreme and permanent mental retardation. This "ruined" state was expressed in local calla dialect as "roont".
Such children would typically grow into powerfully muscular adults, proving themselves useful for tasks requiring brute force, such as pulling plows and other work commonly performed by beasts of burden. They remained sentient and could possess a personality and even a sense of humor, but generally lost the capacity for verbal communication.