Toymaker

"Toymaker" was a term the First Doctor used to describe one of the forms evil took in the universe.

A toymaker was someone who was overtaken by "the urge to create toys that are ultimately destructive", which was, still according to the Doctor, "unfortunately part of our universe". Because "the mind [was] indestructible", so was the spirit of a toymaker. The Celestial Toymaker encountered by the Doctor, Dodo Chaplet and Steven Taylor was particularly powerful, infamous and long-lived, and had adopted "the Toymaker" as his name; but the Doctor grimly remarked that "the world [was] full of destructive toymakers like him". (PROSE: The Celestial Toymaker)

The Second Doctor would later remark on how the Queen of Time had similar proclivities to her brother the Celestial Toymaker's, for all that she preferred to "play with clocks" rather than with literal toys. (AUDIO: The Queen of Time)

Behind the scenes
Although the word "toymaker" in the Doctor's lines about "toymakers" in the plural in The Celestial Toymaker is not capitalised, the vagueness of the concept and of the Celestial Toymaker's origins has occasionally led to the misunderstanding that the novelisation posited that the Celestial Toymaker was a member of a species known as "the Toymakers". This is briefly alluded to in Divided Loyalties, where some of the scattered reports on the Celestial Toymaker in the Time Lords' data banks claim that there were several beings with similar powers, known as "the Toymakers", rather than a single Celestial Toymaker. This is shown to be a misconception later in the novel, with the Toymaker referring to himself as "the Toymaker" in the singular, and identifying his species as a Guardian of Time.