“The Taking of Planet 5”
After facing the wrath of the Fendahl (“Image of the Fendahl”), it is hard to believe that there is a creature out there more powerful than it, but, as The Doctor was to discover four incarnations after his terrible battle with the thing that eats death, nothing can remain top of the food chain forever. Even as the Time Lords locked Planet Five – the fifth planet in Earth’s solar system, located between Mars and Jupiter in the area which is now the asteroid belt – away from the rest of the universe in a time loop, members of the Celestial Intervention Agency recognised the potential of Planet Five as a world where evolution hit a blind alley to create a creature powerful enough to devour the universe. With this in mind, instead of trigging a time loop, members of the Agency instead trapped Planet Five in an accelerated spiral, time inside the ‘loop’ moving at an accelerated rate as billions of years of evolution passed by in seconds while appearing from the outside to be locked in the same few seconds.
As a result of this accelerated evolution, by the time the Fendahl had eaten all but the last form of life on the planet, the last form of life had evolved into something that could kill the Fendahl. Described as a Memeovore, the resulting creature was capable of devouring meaning itself, ‘feeding’ on the subatomic interaction of events caused by observing events as they took place, draining the energy that could result from the multiple outcomes of any event while retaining only its own observation of what was taking place, thus causing the normal-scale cosmos to break down and disrupting the brains of the observers – the most complex structures present, essentially ‘feeding’ on the channels of comprehension that existed between every form of life in the universe.
This creature remained contained on Planet Five for centuries by its relative time frame – how long it remained imprisoned there in the ‘real’ universe is unclear – until it was freed by the actions of a Time Lord platoon currently engaged in the War with the Enemy – a war with an unspecified enemy that the Time Lords would only begin in The Doctor’s personal future (Later revealed to be Faction Paradox led by The Doctor’s corrupted future self (“The Ancestor Cell”), the Faction being apparently ‘replaced’ by the Daleks (“Dalek”) after The Doctor averted the timeline where he became their leader), seeking to release the Fendahl in the hope of using samples from it to create weapons to be used against the Enemy. However, their mission was complicated by the presence of the Doctor, who suspected that something else was happening given that the Time Lords were launching their mission from the home of the Elder Things… a race created by H.P. Lovecraft that The Doctor knew for a fact had not existed.
Correctly deducing that the Celestis – former members of the Celestial Intervention Agency who literally cut themselves out of Time to escape the War and became mere concepts operating outside of reality in the pocket dimension of Mictlan – were behind the creation of the Elder Things, The Doctor took his companions Fitz Kreiner and Compassion to investigate the situation. Encountering a group of Time Lord soldiers from the Future War, The Doctor escaped execution by claiming to be a general in the war while trying to avoid learning any specific information about the Enemy to limit the knowledge he might gain about his future. During their investigation, The Doctor learned that the mission had been infiltrated by a Celestis agent – known to his masters only as One, and, horrified at their arrogance in trying to control the Fendahl, vowed to stop their plans.
Despite The Doctor’s efforts, he was unable to prevent the Time Lords from destroying the time loop around Planet Five by causing a newly-birthed WarTARDIS to crash into the loop around the planet (Another TARDIS created the temporal rift that had powered the time scanner The Doctor had encountered in his previous encounter with the Fendahl when it was shot with a demat gun while trying to escape). As a result, the Memeovore was released into the universe, devouring meaning across the universe before homing in on Mictlan, a manifestation of pure concept that served as its richest feast. As the Memeovore moved to devour Mictlan, The Doctor was able to appeal to the remaining War TARDISes to help him defeat The Memeovore by forming themselves into trans-dimensional blades, essentially cutting Mictlan out of the universe and expelling it into the outer voids.
Although The Doctor guessed that this plan had been implanted by One, he concluded that the plan’s origin was unimportant so long as the universe was safe, and thus never learned why what he had done had been necessary. As One later explained to a member of the assault team, while mating outside Mictlan with an old hermit who became his mentor – it was never specified if there was any connection between One’s hermit and the hermit who taught The Doctor the secret of life (“Planet of the Spiders”), he had become aware of the Swimmers, powerful beings larger than universes who existed in the void between universes, crushing universes as they swam, and had learned that Mictlan might attract the Swimmers to this universe. To this end, he had developed the plan to destroy Mictlan, preventing this universe from attracting the attention of the Swimmers and leaving him and his mentor the last of their people. One’s final fate after the Time War is unknown (Particularly since The Doctor’s destruction of Gallifrey (“The Ancestor Cell”) would have technically erased these events from history).