Doctor Who : The Magician's Apprentice

The Doctor disappears and gives a confession dial—his version of a last will and testament—to his former childhood friend Missy. Missy and the Doctor's companion Clara track down the location of the Doctor before his expected death, and the three are taken prisoner on the planet Skaro where a weak and dying Davros —an enemy of the Doctor and the creator of the Dalek race—seeks the Doctor after recalling an encounter from Davros' childhood.