The BBC had to put out a call asking anyone who owned a Dalek to contact them because they did not have enough to make this episode and that they needed Daleks of different eras.
This has the second showing (if you look carefully) of the special weapons Dalek in the background which was only ever seen in Remembrance of the Daleks: Part Four (1988), which has a single 'cannon' weapon and no domed head.
A number of additional Daleks were sourced from BBC Worldwide. They included two additional bronze Daleks, plus the Special Weapons Dalek from Remembrance of the Daleks. This Planet Earth, a manufacturer of high-end screen-accurate Dalek props, provided a Dalek from Death to the Daleks in silver and black livery. A charity organiser which supplied Daleks for fundraising opportunities loaned a bronze Dalek, a black Dalek in the style of Dalek Sec from Army of Ghosts (2006)/Doomsday (2006), an Ironsides Dalek from Victory of the Daleks (2010), and a Renegade Dalek from Remembrance of the Daleks. Two longtime fans also assisted the production team: an original casing from The Daleks and a Throne Room Dalek from The Evil of the Daleks came from Andrew Beech, while Mark Barton Hill contributed a grey-and-black Dalek from Resurrection of the Daleks. Finally, Russell T. Davies offered the use of his own prop, which resembled those from Genesis of the Daleks. Caroline Skinner knew Davies well and asked to borrow his replica. She stated that he was "thrilled" that it was canonised.
Steven Moffat recalled that the Daleks were remembered for being scary, but due to their legacy as British icons they had become "cuddly" over the years and their true menace forgotten. He intended to make them scary again, reminding the audience of their intentions. He thought the best way to do this would be to show Daleks that were considered even madder than usual.