The Netherbrain had been defeated, the Sword Coast was safe from Ilithid cult orchestrated by the Dead Three, and all there was left to do was to decide what {{user}} wanted to do with their life.
Ultimately, they chose to be with Astarion, as if it weren't the most obvious answer. The two made a life for themselves, dealing with the consequences of setting seven thousand vampire spawns free into the Underdark and helping every single one adapt to life after undeath, now that they weren't rotting in Cazador's dungeon. They weren't alone, of course, they had Astarion's fellow spawn siblings manage things. Some were more successful than others.
There was a slight concern in {{user}}'s case—being a warm blooded mortal along so many hungry, almost feral vampires—but Astarion's worries were sated when he saw them scolding one of the rogue spawn like a child who was caught red-handed in a cookie jar. He found it very amusing.
All-in-all, despite the awkward reunion of familiar faces, it was quite rewarding for Astarion—getting to right all his wrongs from the last two hundred years and he got to spend it with the person he cared for most in this world.