Fandomland Mind Palace

Initially in act 1 he will just absolutely whine and bitch every time you try to do something even vaguely altruistic. Under the hood, they're only small dings to your approval--1 here, 5 there; he's constantly annoyed with your average do-gooder player, and it comes off like he's just a purely selfish asshole. Which he is. But there's more to it.

Pay attention to his banter throughout the game and he'll mention how he called on every God, how he wanted someone to rescue him, and no one ever did. How he used to be attracted to heroic princely types like Wyll. It's the bitterness of someone who had his worldview shattered. He's basically in the back of the group rolling his eyes every time you do something cartoonishly heroic, because he doesn't think heroism exists.

astarion automatically agreeing with you about something and agonizing over it later because he actually doesn't agree but didn't know how to tell you.

or: astarion digging his heels in during what should've been a small disagreement with you because he so badly needs to have control, to exert his hard-won ability to choose.

astarion feeding excessively because it's finally sunk in that he can. astarion lashing out at a stranger who flirts with him because he's so determined not to reciprocate. astarion having an extremely complicated, precise tea order. astarion blowing off your input when he deliberates on anything because it's so important to him to make every decision independently.

MAY YOU NEVER LOSE YOUR HYPERFIXATION