So about that 'epiphany' I had last night... I don’t know, maybe it’s too farfetched. Or maybe someone already saw this before and I’m just late to the party. You folks tell me.
But. My point is
Astarion = Thaniel & Oliver.
The story of the Shadow-cursed lands mirrors Astarion’s divided self, his dilemma, and the choices he'll have to make.
Let me explain (or try to explain, maybe it won't make any sense at all), but first, just a reminder of the discussion with Oliver after the battle:
Doesn't the first part of the dialogue, when he's angry and frustrated, remind you of someone after a certain ritual?
Ok, now let's dig a little deeper...
Thaniel and Oliver are one "person" (nature-spirit embodied in a child) divided in two by the curse.
The one who is surviving through those horrible lands is Oliver, who tricks himself into believing that he is safer on his own, with fantasies(shadows) of his own making for only company in the deepest darkness of those lands. He's not evil, but he's alone and terrified, which makes him dangerous.
On the other hand, the more benevolent, the wisest and sweetest part, Thaniel, is imprisoned in the Shadowfell, unconscious.
And they're both unable to connect with the world. One because he's afraid, the other because he needs to be found and awaken through the reunion with first one.
Astarion is one single individual, but one part of him has been destroyed - or at least silenced - by Cazador’s awful treatments: The empathetic part, the one that saved that sweet man, and for which he was punished. A punishment to remind him that sympathy and a connection to the outside world are weaknesses.
Thaniel/Oliver and Astarion are emotionally damaged, but Thaniel is, somehow, the most “intact part”. The part which was kept “asleep” and therefore, kept rather unharmed from the corruption.
But he's “hollow”, empty… Just like Astarion somehow, who doesn't know what he wants, who he is, even in freedom.
He has to find the person he truly is to fight this emptiness.
Oliver and Astarion are playful, mischievous, but also hurt and fearful. They’re both “cursed” to a certain extent, a curse that affected their body and changed it. And in the case of Astarion, it's not just the "vampire curse", it's also the way Cazador fashioned his worldview. Just like the curse fashioned Oliver, deeply.
Cazador's tendrils also run deep into Astarion's mind...
... Making him believe that there is no one he can trust, no one he can rely on. Through those teachings, Cazador fuelled the "Oliver part" in Astarion, while erasing the "Thaniel part"; That is, the Astarion who's been buried in the ground for much too long, like Thaniel in the Shadowfell.
As for the part of him that still sees the world through Cazador’s rules and lens, it's Oliver.
If Astarion decides to ascend, he chooses the Oliver part. He will lingers in the deepest darkness where he feels “safe”, and his company will be that of the shadows he will create and summons: spawns, wolves and other creatures of the night for whom he will cover the world with shadows.
In those thickest shadows where no light can be seen, he has “everything he ever wanted”. But it’s a lie.
A fantasy he invented for himself; AA is in no way safe, but more than that, he lost himself in the process – just like Oliver who refuses to go back to Thaniel.
He will be alone no matter what. Just like Oliver with his "shadow-family", and who keeps on tricking himself into believing that only those shadows can be trusted.
Oliver sticks to that fantasy because he's convinced Thaniel “couldn’t protect him”, and it is, I think, reminiscent of AA who sees his former self, the spawn, as a weak individual with no worth.
Because empathy, trust, companionship, they're all weaknesses (according to Cazador's rules). So the "softer", empathetic, part of himself, the one who's in touch with the world, can only be a fool, right?
And it's just like Oliver who refuses to go back to sweet Thaniel who, he thinks, failed him.
Oliver, stuck in those shadows, thinks himself stronger than Thaniel, but in the end, he's just terrified, and therefore, dangerous, toxic...
But If Astarion refuses the ritual, he keeps his own Thaniel alive, and finds him in himself.
He reunites his own Oliver and Thaniel. The first one, the part of him that is still influenced by Cazador’s bias, will never completely disappear, but now, it has found the lost part of himself, the one sleeping in the ground, the one who wants to heal, just like Thaniel who will heal those lands...
And put an end to the curse that has been corrupting those lands and inhabitants for too long..
They will coexist within Astarion: the shadows in which he learns to thrive, not as a victim, but as a part of them, and the radiant one, who can inspire hope and cast some light in those shadows.
Therefore, Astarion’s reaction to Oliver running away isn’t accidental.
He recognizes himself in “the little bugger” who wants to hide in the deepest darkness where it feels “safe” (but we know it’s not that safe). That’s why he smiles while watching him disappear. He understands him. He can relate.
But even in act 2, even when Astarion hasn't found his own Thaniel yet, there's still something that stirs in him, an urge, a need to leave the fantasy behind and to have something real, a real connection with someone, and through them, with the world.
Just like Oliver who eventually realises that with Thaniel, he will have a real friend - not just the shadows/fantasies he can create.
Oliver, like Astarion, deeply wants companionship: not people or shadows he can control, but real people he can trust, rely on, and live with.
They both want to feel reality and life, to be part of it and to enjoy it.
And by accepting themselves, all parts of themselves, they'll find a way to really live again. Lights and shadows merging as one.
But it's intimidating.
Oliver is afraid Thaniel wouldn't want him back because he's "changed so much". So does Astarion - the vampire spawn isn't the magistrate anymore. But it doesn't mean they cannot be reunited - emotionally reunited. And for that, he needs someone else's eyes to realise that he is, as a vampire spawn, worthy enough.
The way you see him helps him restore himself, just like you helped Oliver and Thaniel accept each others again.
On the other hand, when you tell AA how much he changed, the only thing he has to say about it concerns his new powers. Nothing about emotions, personality, etc.
He has lost touch with himself - he's only just power and shadows. He doesn't seek who he truly is or wants to be. He has lost "his Thaniel". Like Oliver, he keeps the whole world at arm’s length, and he gives into those fears, just like Oliver would do without you – he sticks to the idea that the whole world is a threat, and that he can protect himself from it only by covering it with shadows, and by surrounding himself with phantoms he controls entirely. It’s not life. It’s a prison of his own making, just like Oliver’s Shadow-cursed Lands.
Without the Ascension, just like Oliver and Thaniel needed Halsin’s gentle care to be reunited, to find Thaniel in the Shadowfell, Astarion needs Tav/Durge’s patient attention to walk back to his true self, to find the one buried in the ground.
It takes a few efforts, but it's not impossible.
And only if he accepts to find his true self, hope can start blooming again.
The progression of each of the acts’ storylines in BG3 is insane because it’s just like
Act 1: There’s a bunch of goblin cultists trying to kill some druids because they believe in a different deity, kill them so the refugees can leave safely, or turn on the druids and refugees if you want to play as a bad guy
Act 2: A bunch of people have been kidnapped so you need to venture through the British countryside of Perpetual Night to kill this lich with the help of his lesbian daughter and her demigod girlfriend in order to revive an immortal child that was banished to the Shadow Realm
Act 3: A gnome terrorist organisation will help you blow up a giant robotic policeman so you can go beat the shit out of an Archduke after you find out his anaemic spy’s underlings have been murdering people from the local brothel before you go to soufflé a giant psychic brain deity so everyone doesn’t turn into evil squid furries.