Out of the ten known characters available to romance in Baldur's Gate 3, the High-Elf Rogue Astarion remains one of the original options seen from the game's Early Access. The spawn of a vampire, Astarion, can you as a companion after speaking to him southwest of Roadside Cliff near the Nautiloid shipwreck on the beach. Building Approval with this character could lead to a growing affection if you make the right choices.
Any companion character can become friendlier to you by gaining their Approval through certain actions taken throughout Baldur's Gate 3. Astarion enjoys it when the player takes advantage of others, fitting into his previous position as a manipulative creature of the night. Being deceptive and uncaring are ways for Astarion to take an interest, leading to a good relationship that can blossom at a certain point in the game.
How To Unlock Astarion's Romance Scene in Baldur's Gate 3
The romance scene with Astarion comes after you save the druid Halsin and finish the side quest to save the refugees near the Goblin Camp in Baldur's Gate 3. Taking a long rest leads to a celebration for the refugees, where Astarion will be close by for your character to talk to. However, it would be best to speak to Astarion before doing this set of quests, not only to learn more about him but also to build more Approval if you can.
Since Astarion is a vampire spawn, allowing him to feed on your character's blood in an earlier scene is a great way to build enough Approval to make his romance scene available at the party.
When talking to Astarion at the celebration, he will mention his dislike for being considered a hero for saving the refugees. Your character must respond with, "Really? Saving lives is awful?" before he speaks more about the party itself. From here, mention how the goblins would have thrown a better party and ask Astarion his idea of "a little fun."
Astarion will suggest that he and your character could have fun together, which will cause him to show up when you go to your bed. You should now have the choice to spend the night with Astarion, which leads to another interaction. Some dialogue options here can further strengthen your relationship with Astarion, like saying, "You don't have me yet." and asking what the vampire spawn wants.
Being agreeable and respectful to the Rogue gives you the romance cutscene for Astarion and your character, which could develop into an even stronger bond with the official release of Baldur's Gate 3.