The Sontarans and the Weeping Angels have come to Earth in Doctor Who season 13 - and their presence there may be connected to the Flux itself. With production disrupted by the coronavirus pandemic, Doctor Who showrunner Chris Chibnall has decided to pursue a different approach for season 13. This is an abbreviated, six-episode series with a single overarching narrative, as the Doctor wrestles with the mystery of a cosmic event known as "the Flux."
Doctor Who season 13, episode 1 set up the drama in an adventure on an unprecedented scale. According to the Doctor, the Flux is a cosmic phenomenon that disobeys every law of time and space, disrupting matter on an atomic level. It does not seem to be a natural event; rather, it's a weapon wielded by a being who calls himself Swarm, an old enemy of the Doctor whose existence has been erased from her mind by the Time Lords. The Doctor is at something of a disadvantage, because Swarm knows all about her - all her tricks, all her tools, all her strategies - while she has no idea who he is at all.
In addition to Swarm, Doctor Who: Flux features a number of other alien threats. The season 13 premiere showed Weeping Angels already present on Earth, preying on human beings around Liverpool. Meanwhile, the warlike Sontarans are preparing an attack - and, given episode 2's trailers show the Sontarans fighting in the Crimean War, it's safe to assume they're invading Earth. What does all this have to do with the Flux?
Both the Sontarans & the Weeping Angels are Time-Aware
The Time War between the Daleks and the Time Lords caused havoc on an unimaginable scale. As the Gelth explained it to the Ninth Doctor in "The Unquiet Dead," "The whole universe convulsed. The Time War raged. Invisible to smaller species but devastating to higher forms." Most time-aware races were wiped out during the Time War, with only a handful of exceptions - and it's interesting to note both the Sontarans and the Weeping Angels number among them.
When the Sontarans were introduced in 1973's "The Time Warrior," one of their number had been stranded on Earth in the Middle Ages, and used primitive time travel to kidnap scientists from the future to help repair his ship. In 1978's "The Invasion of Time," the Sontarans actually managed to launch a near-successful invasion of Gallifrey. They sat the Time War out, complaining they were forbidden to join what they considered "the finest war in history." The Sontarans apparently have prior knowledge of the Flux, recognizing it as the beginning of a far greater conflict, and they're excited at the chance to participate in this particular war.
The Weeping Angels, meanwhile, have a biological connection to temporal energy. They are typically isolated predators who transport their victims backwards in time, and then feast on the temporal energy released by the resulting paradoxes. They seem to have an innate sense of major temporal events, identifying the TARDIS and attempting to break into it in "Blink," and fleeing from a crack in spacetime they sensed could destroy them in "Flesh and Stone." Where the Sontarans have intelligence of the Flux, it's reasonable to assume the Weeping Angels can sense it as a cataclysmic spacetime event.
Why Weeping Angels & Sontarans Are Coming To Earth
Both Sontarans and Weeping Angels are time-aware, meaning it makes sense they would have an awareness of the Flux, which seems to be a major spacetime event of some kind. The Weeping Angels would naturally fear the Flux, sensing impending destruction, and they could therefore have come to Earth as they flee from the cosmic phenomenon. For their part in Doctor Who: Flux, the Sontarans seem to have come for conquest; they evidently believe Earth will lie at the center of the conflict surrounding the Flux, and they're eager to participate in it. Having sat out the last great Time War, they're not going to sit back and watch other races go to war any longer.
This naturally raises a curious question; why would the Weeping Angels and the Sontarans, aware of the impending cataclysm, choose Earth? It's likely the reason is a simple one; although the Doctor will fight to save any world, she has a special fondness for Earth. As seen in Doctor Who season 13, episode 1, even though the entire universe is being destroyed, the Doctor will still focus on saving the Earth first. Thus this little blue planet in the Milky Way will become the last world in the universe, the only place that is safe from the Flux - at least for a time. If this theory is correct, then the Weeping Angels have come to Earth to seek sanctuary, while the Sontarans want the last planet in existence to belong to them.
How the Weeping Angels & the Sontarans Could Help the Doctor
Doctor Who: Flux episode 1 ended with the Doctor, Yaz and Dan trapped in space, with the Flux invading an apparently dying TARDIS. It's one of the biggest cliffhangers in Doctor Who history in terms of sheer scale, but the show isn't even trying to pretend its stars won't survive somehow; they've even already met a woman they're only destined to encounter in their own personal futures. Clearly, then, the Doctor and her fam will make their way back to Earth, only to discover the Doctor's favorite planet is now home to Weeping Angels and Sontarans.
The Weeping Angels have never been especially communicative, so the Doctor isn't really going to learn much from them; rather, they're most likely predators she needs to outsmart. But the Sontaran battlenet evidently contains information about the Flux, perhaps even records of the Doctor's forgotten battles with Swarm. If the Doctor can access their records, she will be able to learn a lot about Swarm and the Flux, perhaps even giving her a chance to defeat them. The Doctor has always had a habit of turning her enemies against one another, and it would be so very appropriate for her to figure out how to use the Sontarans to her advantage in Doctor Who season 13.