Prologue: The Sixth Doctor (comic story)

The Sixth Doctor and Mel run up to the Inquistor and inform her that the Valeyard has just escaped into the Matrix and must be brought back. The Inquisitor agrees, allowing the Doctor to open up the Seventh Door. Mel hesitates, feeling that something is wrong. The Doctor waves off her concern, thinking she is talking about the Valeyard. The two run into the Matrix, only to find that it has been taken over by the Cybermen.

Characters

Worldbuilding

The Doctor claims that the fact the Valeyard exists is "an abomination against the Laws of Time", and that "history itself is warping."
The Matrix appears as a version of London with Big Ben.

Notes

This story was published in 11DY2 11.
The Cybermen in this story appear somewhat similar to the "Cybus" design introduced in 2006 but with certain cosmetic changes. Most notably, their chestplates have been replaced by clocks.

Continuity

The events seen here are a result of the mass invasion of time and space by the Cybermen, who have allied with Rassilon. (COMIC: Supremacy of the Cybermen)
The events of this comic are an alternate version of some of the events that occurred at the Sixth Doctor's trial. Differences include Mel's clothes and hairstyle, the fact that Mel went with the Doctor into the Matrix, and the fact that Sabalom Glitz, who was the one who originally went with the Doctor into the Matrix, and the Keeper of the Matrix, who was the one who provided the key to open the Seventh Door, are absent from these events. (TV: The Ultimate Foe)
This perversion of history is ultimately negated when the Twelfth Doctor and Rassilon restore the timeline. (COMIC: Supremacy of the Cybermen)