I've never been interested in romancing Astarion, but the Ascended kiss interactions actually made me curious to try it out. Good writing is not always convenient writing.
You may be disappointed. Ignoring the fact that Tav's response is a huge turn off for some of us, Astarion's attitude in those animations isn't seen elsewhere in the game; it's very much out of character. Astarion's personality does become more domineering but it's clear he still cares for Tav and that Tav has autonomy within the relationship. eg: Tav can still break up with him. If you are looking for a 'romance' relationship story with Tav and a sadistic vampire who controls them against their will, you aren't going to get it.
Originally Posted by LiryFire
Astarion gets so triggered when he's called a Cazador. He has a temper, he has darkness in him - but it's different. He is not dictated by anything other than his personality. That's why he's letting Tav and Karlach go. It makes him feel better if Tav's into it. That's why Astarion says "live your best life, even if you don't appreciate it" - it shows how he is even in the illogical Angst-Tav line. More fun for such people is a faithful spouse who understands and trusts. An evil kindred spirit. Face victim-Tav is wrong on just a few levels.
