0_o As always, your writing is as enjoyable to read as it is creepy.
While being Xykon's favourite pet is likely to stop anything too bad happening to Tiasal, I'm now worried about what will happen if anyone does try to rescue her. Unless she gets significantly more powerful before then she herself wouldn't be a threat, but I could all too easily see her causing a rescue party to be caught. Especially if she underestimates what Xykon would do to them. *shudders*
Also, who is that talking in the non-italic dialogue at the beginning of the second chapter? The only thing I can come up with is that it's the cleric talking to himself.