Hot News February 2024 - The Ascended is not a different person, the same person, same Astarion. (which was obvious enough, but still) He hid his evil part under a goofy mask - his VA said, he played him that way. He's showing all his problems. He becomes honest about all his desires, especially his evil desires. That's exactly how I felt. The big Astarion inner evil train is coming.
And that's the problem we can't explore the evil of Astarion before the ritual in Act 3, see it. Only the Ascension reveals it to the player.
It will be helpful to have the mask cracked a bit in Act 3 before the ritual. As another option after to keep track of everything - after the ritual in both path.
Honestly his past will handle this just perfectly. It'd be funny if romance did it too.

Yes, having a player with him in an affair should reveal other things to us. Work the romance in Act 3 before the ritual and for Spawn would be great. Lord Astarion has more lines, but he could use content too. (I personally want to do evil romance with all Astarions)