Confession dial

A confession dial was a small, circular disk containing the last will and testament of a Time Lord. According to ancient Gallifreyan tradition, it was to be delivered to their closest friend on the eve of their final day. (TV: The Magician's Apprentice) It was used to expose someone to their greatest fears and then make them confess; if the person did not confess they would be killed. (TV: Heaven Sent)

After being summoned by Davros, the Twelfth Doctor left a confession dial with Ohila for her to deliver to (WC: Prologue). Missy brought it to Earth and met with Clara Oswald, and explained that the confession dial was to be given to a Time Lord's best friend prior to their death. Clara attempted to pick the dial up, believing that it was intended for her, but it responded by shocking her. Missy explained the confession was for herself, and would only open after the Doctor died. She took it with her to Essex in 1138 and to Skaro. (TV: The Magician's Apprentice)

Davros came into possession of the dial after he and the Daleks took the Doctor, Clara and Missy prisoner. When the Dalek city was destroyed by decaying Dalek mutants revived by regenerative energy, the Doctor took back the confession dial. (TV: The Witch's Familiar)

The Twelfth Doctor gave the Confession Dial to Mayor Me just before Clara Oswald's death in the trap street she governed. (TV: Face the Raven) He himself was subsequently teleported inside it, where he was pursued by a veiled creature from his nightmares which sought to force him to confess his knowledge of "the Hybrid". After entering into a recursive loop of dying and reloading himself from the teleport's hard drive that lasted for at least two billion years, he finally broke free and passed through a portal to outside the device, and found himself on Gallifrey. (TV: Heaven Sent)