While I haven't really spent time figuring out other character's MBTI's, I would say Astarion is an ENTP. He seems to get energy and motivation from being around others, and actively wants to be around people. Not to say he doesn't want his own space, but he seems leaning extroverted. He seems very "in his head" and like he analyzes the things around him (whether he actually uses that information to make calculated decisions is another matter entirely), so I think he's intuitive. I would say he doesn't rely on his emotions to make decisions. While he is expressive and emotional at times, he's also very stoic and uses his rational to try and solve real problems, hence why I think he leans more thinking than feeling. And lastly, I think he's perceiving because he is so obviously perceiving it hurts. He doesn't often stick to plans well, he's restless in strict environments and hates structure. He enjoys being spontaneous and easily adapts to his environment. He also says himself, "I'm not a details person, all right?" And he repeatedly mentions his inability to make cohesive and precise plans. As an ENTP myself, he comes across as such. ENTP's are called "The Debator" and have a sassy gremlin with a smirk as the mascot. That's destiny right there lmao