In the 26th century, Dalek Killers (also called DKs) were criminal citizens of the Earth Empire who were given a chance of having their sentences of death by vaporisation commuted if they fought the Daleks, with miniscule odds of survival. The Earth Empire judiciary offered, as an alternative to execution, the chance to choose from a wide variety of weapons prior to teleportation to a Dalek Empire planet, where they would do their best to survive. The Daleks addressed the War Doctor as the Dalek killer during the Last Great Time War. (PROSE: Engines of War)