Dalek Tapes

The Dalek Tapes were a comprehensive collection of tapes that documented the history of the planet Skaro. The Doctor discovered them after landing in a mouldering, ancient library on a twilight world.

The first tape told of the early mystery of the Daleks in their humanoid form. There were at least seven tapes, with the seventh telling of the Daleks' encounter with the Monstrons. At the conclusion of this tape, its narrator stated that the Daleks continued to spread their evil throughout the galaxy in the ensuing years. (COMIC: The Dalek Tapes)

Behind the scenes
The Dalek Tapes served as the framing narrative for the reprinting of The Dalek Chronicles in Doctor Who Magazine. This occurred in 1980, sometime after the broadcast of Genesis of the Daleks which claimed that Davros was the true creator of the Daleks. As such, the added context is vague enough that the tapes could have been corrupted in their old age or plain wrong on the part of the narrator, casting some doubt on what was once the sole Dalek origin story in favour of other existing versions.