Alright, let's go section by section here.
Dragons: The dragons will get more time, and their annoyance will depend on which you're using. Vahruna is obviously the most sociable, but Velonir will be rather ambivalent. Not to mention don't be expecting any meaningful bonding time with Voxoron.
Isabella: Will probably take a back seat, at least for now. She will be around and be involved in the tower, but probably won't see a lot of action at the moment. (Unless I can talk Kthu into the Mida threeway of my dreams....)
Katla: We'll also have her around, but since she has been clear that she can't look past the Mother/Son relationship with him, don't expect any thing more than that. That said, I've had ideas on how to use her and her position in the tower.
Jendayi: Jen is my character and so something I struggle with. Obviously I have a much easier time with Cerea, but Jen is a fine line for me. Part of me loves her cute, naive charm. She takes to the little sister role in the tower and hasn't seemed interested in returning to her Centaur form. I feel like she's a tiny bit "Little Mermaid" inspired. Just don't expect a musical number. That said, I have problems with what I want to do with her. Her main trait with the MC is adoration... which could turn kinky, but I have a hard time perverting her because I almost want to lock her in a glass case and keep her cute and virginal forever. I also think it's long overdue for the MC to visit the Centaur leaders with her, but I haven't planned out the Why and What in my head yet.
Cerea: For those of you wondering about the "Mind Breaking" it was pillow talk. First off, it'd be near impossible to break that mind. Secondly, he doesn't have Father's Corruption ability anymore. Now if you corrupted Calessa, that's forever. But Cerea won't be breaking any time soon. However, if you're on the Rent path, she may be very much willingly become your pet... Just gotta find that Sex Dungeon...
Kat: Kat is my favorite of Kthu's original characters and she's why I wanted to start writing for him in the first place. She lets me express my smart ass nature, both with her lines and his and how the two of them play off each other. And no, Kvlt will not be attacking her. They didn't even go outside. Right now she knows (roughly) how to get to the Baths and the Lab. We haven't even found her a bedroom yet, or shown her where to get food. She wouldn't even know the front door to go out it. But yes, she will get registered, not to worry. As for Ayna, if she wants her back so bad she'll just have to come to the Tower too to get her.
Ataegina: Not up to me.... she's all Kthu's domain. But the room you found her was entirely from my head. As was the Treasure Room...