The Daleks were using one of their spaceships for the Parliament of the Daleks. On board were thousands of Daleks under the command of their Prime Minister. Drone, Strategist and Supreme Daleks made notable appearances as well as the Time War bronze Daleks. The Doctor recognised the Parliament of the Daleks spaceship which suggested he’d been there before.
The Prime Minister is in charge of the Dalek Parliament. The Dalek Prime Minister appeared outside of a Dalek casing. It was just the Dalek creature in a glass cylinder structure with no visible weapons attached to it.