Syldyr’s partners from my pov as the player:
Astarion - the originally-intended romance partner b/c I heard he had a lot of durge-specific dialogue and I wanted to see that, but then said dialogue had them relating so much that I was like ‘well fuck this DOES work really well’, so I committed and he was Syldyr’s “canonical” end-game romance for the playthrough
Karlach - wanted to romance her from the get but my previous playthrough my friend romanced her so I was curious this time around, ended up thinking a LOT about how sweet Syldyr’s connection with her was and couldn’t shake it after that (she’s the only one that actually kinda listens to durge when you tell her about the murder impulses, and Syldyr was craving someone to believe him and ground him in reality. she saw who he was, what he was, and still believed he could be good, and that cut straight down to Syldyr’s soul (aka right in the backstory))
Gale - appeared in the Act 2 durge scene instead of Astarion as an accident of the relation progression system (game ended up counting Karlach and Gale as my two active romances even though I had already spent the night with Astarion in Act 1, I think just because their approvals were just slightly ahead of Astarion’s, and then when I had to turn down Karlach b/c no poly in base game, Gale was next in the romance & approval line-up), but decided to play through it anyway as feelings Syldyr hadn’t acknowledged yet, and then the following scenes with Gale ended up working so well and sucker-punching me in the heart so hard that I could no longer pretend that Syldyr wasn’t also deeply in love with Gale