Consistently chooses to deal with his feelings on his own instead of with others; if you tell him the Rite of Thorns has completed, he says he needs to go be alone. In the deleted scene where you could collapse his portal, he would have gone off to be alone before leaving the party. He mentions after the Shadow Curse that he'd became fond of lonely nights alone with honey mead.
Laments his lack of peers, stating that his forced leadership role stole away the few the Shadow Curse didn't kill, and even cites this as part of the reason he began to "gild undeserving memories of his youth" and romanticize being a sex slave as he had been before.
Wants a family, but hasn't had one, and seems to think during the main game that his chance his slipped him by due to how much time he spent as Archdruid; also misses his birth family who died years ago.
Is adored and revered by some of the Druids, but hated by just many, seen as weak, ineffectual, and even the cause of them not being able to fight back the goblin armies.
Is blamed by the Tiefling refugees for what happened, or at least associated with their trauma so much that if you control Halsin in act 2 and attempt to speak with them, they refuse to talk to him.
Has had unique traumas that the other tadfools don't always understand, being frustrated at times with his laser-focus on the Shadow Curse, and sometimes not understanding the significance of him saying he won't drink except on very special occasions anymore (despite being very well-meaning when they suggest breaking his dry streak).
Was lonely enough, and not seen for HIMSELF enough, that just journeying with you is something he cites as one of the happiest, if not the happiest, time of his life (the note he sends you in the epilogue if he's left behind in the Shadow-Cursed Lands; his Speak With Dead dialogue if killed by Orin)
Repeatedly relies on you as the player for physical safety (rescue from the goblins, protection from the portal, potentially rescuing from Orin), emotional intimacy whether romantic or platonic, sexual intimacy if the player is interested, and the ability to be himself and be pulled from what he describes as the "fog" that fell over him with the Shadow Curse (which ftr is absolutely a metaphor for depression, almost all of us who have had it will describe it the same way)
Loves you so much if you pursue a relationship and yet doesn't believe for a moment you'd actually want to go with him to his new commune, to the point of treating it like a forgone conclusion that you won't and being completely taken aback when you say of course you're coming; even after living together for six months, he still believes you don't actually want to stay with him forever, and that the instant seeing your old friends reminds you of your adventuring days, you'll want to run off again and leave him behind. (And yet despite this, despite being in agony about it, he STILL comes without hesitation, both because he wants to see his old friends too and because he knows that even if you do decide you want to leave, he has no right to stop you.)
In short: Halsin has been isolated for so much of his life, and is so used to being left behind (willingly or not) that he just doesn't have a framework for a happy long-term relationship, and is unused to being able to rely on others to fulfill his emotions or social needs until he meets you. You aren't just a lover- you're his family, the first person to show him care in a VERY long time.
Like no wonder he loves and needs you so much.
