Thaxian (vampire bat-like shape changers) Slaugth (maggot men) Thyrrus (artistic tentacle monsters) Q'orl (formic) Xenarch (best guess, mineral monsters) Fra'al don't have any images beyond their badass ships, but most assume they look like Greys. Made me a MONSTER MASH!
...You didn'.... No. No, you sure did. Unless the Necrons developed a code to neutralize them, they'd likely take over the galaxy, as the Eldar may find them too 'primitive' to be able to find the means to scan their coding and neutralize it, the Tau would be massacred, leaving only the IoM tech-savvy enough to try and study them, their code and ..oh wait, that would be heresy. So basically, unless Necrons, Replicators.
I can think of three things of the top of my head. They end up going after the Necrons, who either enslave them or hybridise with them. They find STC systems and end up resurrecting The Men Of Iron. They come in contact with the Adeptus Mechanicus and end up as part of a Heretical Cult of them that worships the human form Replicators. You could even have all three as different, and opposing, splinter groups happening at the same time. I'd be more interested if these guys turned up:
Thing about Doctor Who is they never really use weapons against the enemies do they, at least the protagonist doesn't So I dare say plasma/bolt shell will destroy a Cyber man
They have weapons that a normal human can Carry that oneshots cybermen, even the super fast upgrade ones
But he problem is that digter who is filled with dues ex machina Stuff on both sides, allways something dues ex machina
