I know them feels, CJ.
I always try to write in antagonists into my characters back stories. Usually I try to aim for a smallish organization or even just a rival (a Gary Oak to my Ash, if it do ya), but it doesn’t always end up that way.
The most disastrous of these attempts was when I wrote into my cleric’s back story that his father ran a mage school, and was in league with the elves from O’lithius (the same ones I mentioned in my update regarding the mountain). At the time, I didn’t think anything of it, I figured we’d have to stop him, but it wouldn’t be anything too crazy.
I was terribly wrong.
For one, it turns out that my father was actively helping the elves setup shop on the continent. We relied on his help to try to stop the elves (without knowing that he was actively giving us bogus info on them), and eventually he became a central villain in the last major storyline we did involving the elves (he was one of the big names we were supposed to take out). Unfortunately, we never got our shot at fixing my mistake, as we scored ourselves a TPK before we had a chance to face him.
I think I’ll stick to adding a small pet into my back story next time, probably safer that way.