The Toymaker's ring

The Toymaker wore a "large sapphire ring" on the middle finger of his left hand.

History
The ring appeared to be key to the Toymaker's power, as he used it to manipulate the various elements of the Celestial Toyroom during his match against the First Doctor, Steven Taylor and Dodo Chaplet. The Toymaker used it to enlarge his clowns from inanimate toys to human-sized talking, moving beings, and also to make one of the Toyroom's walls vanish to reveal the conveyor belt of duplicate police boxes he had created to prevent his "guests" from easily escaping in the Doctor's TARDIS. When the Toymaker used his ring, it emitted "concentric rings of blue fire". (PROSE: The Celestial Toymaker)

Behind the scenes

 * The Toymaker's ring and its mysterious properties are reminiscent of the First Doctor's own signet ring. It was the original intent for the Toymaker that he may be a powerful member of the Doctor's own kind, although this idea was never made explict in a narrative context.
 * The Toymaker's ring was added only for Gerry Davis and Alison Bingeman's novelisation of the story, and does not appear in the televised version. The surviving fourth episode, "The Final Test", clearly shows that Michael Gough wears no sapphire ring (or any other jewel) as the Toymaker.