The new Dalek army was led by a Supreme Dalek , who kept Davros imprisoned in a `` Vault '' ; Davros said that he and the Supreme Dalek had reached `` an arrangement '' . The episode depicts a Dalek invasion of Earth led by Caan , Davros , and a red Supreme Dalek , who has kept Caan and Davros imprisoned in `` The Vault '' , a section of the Dalek flagship , the Crucible .