Buffy belongs to Joss. Gene Roddenberry created Star Trek. (Q is his creation, though I'm not sure which Trek writer deserves the credit for the female Q.) I just like to play in their sandboxes now and then.
She was profoundly bored. She didn’t really understand what Q or Q saw in this backwater of a minor planet and its insignificant bipedal hominids. They hadn’t been around long enough to be interesting; they were practically still monkeys. At least they were still confined to their own planet. Mostly, that is. There were a few that traveled to other dimensions, though usually not intentionally, and often with the help of the non-human population.
She was monitoring one of the few slightly interesting regions of the planet, a town on the western coast of one of the major landmasses that happened to be situated above a dimensional convergence. Most of the humans that lived there were blissfully unaware of that fact. The ones that knew about it worked very hard at trying to keep it that way.
She had toyed with the notion of telling them all that was to come, which to a member of the Continuum was as plain as if it had already been written. She had decided against it, if only to prevent the cleverer of the humans from waging war on the Powers, those officious busybodies who took it upon themselves to ‘keep the peace’, whatever that meant.
Besides, unlike the other two members of her species who dropped in on this benighted planet from time to time, she rarely broke the self-imposed rules that governed the interaction of the Q with lesser species. She was willing to make an exception just this once, however.
The situation was interesting, mostly because whether they liked it or not, the Continuum was already involved, if only tangentially. What had possessed those idiot monks to channel the Key into sentient form, and a mortal one at that? Especially knowing that even the Powers’ favorite tool, the Slayer, would be unlikely to stand against a higher being like the one calling itself Glorificus for very long.
The Q hadn’t needed the Key for billions of years, but it still irritated them to have someone else steal something they had created. By rights, she should swat Glorificus like the insect it was in comparison to the Q. There was no way she would allow the chaos that would ensue if the Key was used in an uncontrolled manner as the would-be godling intended. But it did amuse her to see the Slayer and her allies fight on their own, particularly once they discovered the way they could win.
Unfortunately, Glorificus had allies as well. One of the non-humans succeeded in accessing the power of the Key. The now human Key had no idea how to control its power, and the only way it knew to close the uncontrolled dimensional tear was to destroy itself completely. That was unacceptable. Not because it involved the death of a human, but because it meant the destruction of Q property without their consent.
Over the course of their long existence, the Q had learned that even small actions could eventually have huge repercussions. Q considered all the possible futures that could result from the available options. It took only a few fractions of a second for her to determine the right course of action. She didn’t even need to appear in human form for this. The smallest inspiration, a mere suggestion, and the Slayer would do the rest. The Key would remain alive, and human- for the time being, at least.
But now it would eventually come home. The Continuum would thank her for it in due time. Who knew, it might even be the change Q kept telling everyone was needed…