One of the first dungeons that you might clear in Baldur's Gate is the Necromancer's Basement in the Blighted Village, right under the Apothecary. One of the defenses of the place is its magic mirror, which was "enchanted to present a nice appearance, but with the wretched personality of its owner", and one of the ways to bypass its defenses is by answering a series of questions that prove your affinity with the owner of the mirror.
One of the questions that the mirror asks is "If you could see anything in me, what would it be?" and each of the Origin characters gets three possible answers (as well as three unique possibilities for Custom Tavs). As these characters are talking to a mirror -- in a narrative and metaphorical sense they are talking to themselves, and so they have no reason to lie. If the tale is well constructed, that means that each of these answers represents a deep-seated want, need or ambition of each Origin character -- one of the ways that they might succeed or fail in their storyline.
There are some surprises and some truly moving and some horrifying revelations (GALE I'M LOOKING AT YOU).
Tav
"Tav, if you could see anything in me, what would it be?"
1. I'd see the ones I love.
2. I'd look for whatever spell will rid me of this worm in my head.
3. I'd see my enemies suffering.
The Baseline, and the situation that you might have encountered the most. It presents three options: one based on love, one on survival and one on revenge / power. If you want to survive, pick the one that evokes immediate survival to you.
Lae'zel
"Lae'zel, if you could see anything in me, what would it be?"
1. I'd see myself as a kith'rak: ghaik head in one hand, silver sword in the other.
2. I'd see the zaith'isk, the purifier - a relic used to extract a tadpole.
Forever practical, Lae'zel only has two possible answers: she wants to either become a kithrak with her very own dragon (you go, girl!), or to locate the relic that will rid her of the parasite.
Surprisingly, nothing about Vla'akith. She's pretty chill and down-to-earth.
Shadowheart"Shadowheart, if you could see anything in me, what would it be?"
1. I have no memory of my parents - I'd like to see them, at least once.
2. I'd see myself as Shar's Chosen, with all her powers at my disposal.
3. I'd see those who'd tormented me in the past receive the same.
Shadowheart wants to either get her memories back - specifically, her memories about her parents-- or hurt "those who tormented her in the past. As her tormentors are probably the same clerics of Shar who educated her on mental torture, etc. this creates an interesting conflict of interests for Shar.
This also suggests that Shadowheart's parentage is going to be key for the story, although it would be kind of cool if it was reversed like for the five minutes that The Last Jedi lasted.
Astarion
"Astarion, if you could see anything in me, what would it be?"
1. I'd see my home. My real home - the one I haven't seen in centuries.
2. I'd see how to safely keep the powers this mind flayer's worm has given me.
3. I'd see Cazador, my old master, burning in the sun.
For Astarion, the most innocuous, sweet, relatable answer is the one that he keeps hidden -- throughout the game, he's VERY vocal about "controlling, not removing" the tadpole and its powers and destroying Cazador.
The biggest surprise here is that Astarion very badly wants to go home. But where is home? Is it a house within Baldur's Gate, or rather an entirely different place?
Gale"Gale, if you could see anything in me, what would it be?"
1. I would see a wizard tower. A safe haven for me and a sweetheart - forever.
2. I'd see myself in my next incarnation: a living manifestation of Netherese magic. A mythal in my own right.
3. I'd see my rivals humbled - jealous of the majesty that I've become.
Ehm so Gale either wants to have a wite picket fence and a sweetheart OR he wants to become a Netherese monstruosity.
No mention of the tadpole! Maybe he's feeling pretty sure that whatever the Illithids did to him, it will eventually get devoured by the Void he carries, and he's tagging along with the party to acquire more artifacts and / or reach the Astral Plane / Netherese areas.
No mention of Mystra either. I don't know about you guys, but these are the answers that chill me to the bone.
Wyll"Wyll, if you could see anything in me, what would it be?"
1. I would see my father - his arms extended in forgiveness.
2. I'd see Mizora, cowered before me and begging my mercy.
3. I'd see dorves of admirers, gathered to hail the Blade of Frontiers.
No surprises here -- Wyll clearly wants to reconcile with his father, get rid of his dependence on Mizora (although she's just a symptom of what he will try to do to get that admiration, not really the cause) and be universally adored as a hero.
The father issues and limelight love are connected, while his wish to hurt Mizora is just self-hatred at his own perceived weakness; that's his dark side.