I will often use swear words with Rhaya, myself. Especially 'hells', or 'seven hells'. (Though I did once use Hells Bells and immediately corrected myself. I'm not a wizard detective x.x)
Generally, I find it's best to use what you have seen the NPCs use, but occasional usage of things they haven't said is perfectly fine in my mind. I've been guilty of dropping the f-bomb from time to time, myself.
Ultimately, I find that as long as you do your best not to break immersion, and it makes sense at the time, you should feel free to use swear words to your heart's content.
Generally, I find it's best to use what you have seen the NPCs use, but occasional usage of things they haven't said is perfectly fine in my mind. I've been guilty of dropping the f-bomb from time to time, myself.
Ultimately, I find that as long as you do your best not to break immersion, and it makes sense at the time, you should feel free to use swear words to your heart's content.
