According to Lozz, the kids ran the streets of the Kaballus Quarter.
The librarian of the Renath Archive, Matildus Galathea, allowed the kids to hang about there. She read them stories and gave them Grovian doughnuts. One day Matildus began acting strangely and barred the kids from the library. Several months later, they saw Bill Potts leave the Renath Archive, the first person who did so for months. Looking for answers, the Kaballus Kids captured Bill. Bill showed them a photo of Matildus being grumpy, which revealed something strange around her head.
Returning to the library with the Kaballus Kids, Bill told the Twelfth Doctor, Matildus and Sashana to stop whatever it was they were doing. Bill took a photograph on her phone which revealed Sashana's true form. Sashana revealed that she was psychically sowing doubt in Matildus' mind and blocking her memories so Sashana could sell off the library's collection after being handed custody. She began to fry the group's brains with her mind, but was stopped after Bill summoned Archie, whose simple brain couldn't be kept back. While Matildus believed that she had no family, the Doctor disagreed, pointing to the kids playing in the library. (COMIC: Matildus)