Dalek (The Power of the Doctor)

A Dalek betrayed their kind during the events of the Master's Dalek Plan. It believed that the creation of the Daleks was meant to protect the Kaled race but that the Daleks had fallen too far from that. It contacted the Thirteenth Doctor to reveal their plans, unaware that it was being manipulated by the other Daleks to bring the Doctor to them. Upon arriving, the Dalek allowed the Doctor to copy information from their casing before three other Daleks including their commander arrived and killed the traitor.

After the Dalek mutant inside had died, the Daleks imprisoned the Doctor in its casing and took her to 1916 to be captured by. (TV: The Power of the Doctor)