The worst part about Karlach's death for me was, that I couldn't keep my promise to her and instead of being at her side, had to hide from the tyrant sun in the shadow of some crates.
Halsin isn't for me either, he's alright as a npc or neutral-approval companion who sits in camp and whittles. But I do like Minthara and am very glad we can now save her on goodish runs. Her dialogues are among the most memorable in the game and her recruitment at Moonrise along with her retelling of how she got trapped by the Absolute are the game's best horror moments. I wish Durge had the intensity of Minthara's tale.
It's also nice that the start of Minthy's romance can double as a scene of friendly bonding. Especially with Gale, Lae'zel and Shadowheart I enjoy the conversation because I think they can relate to having their destiny laid out for them at an early age. Talking about Shadow, I like the wine scene with her. For Avatar-Astarion and -Gale it's nice because they are given an opportunity to talk with a friend about their past, and for Avatar-Lae'zel the scene is plain adorable.
Ketheric is great too. I love how absolutely done he is with everything.
My first reaction to the mirror scene was wanting to get Gale to cast a modified mirror image for Astaion.
Especially when I am plaining the people-pleasing wizard as my player character, I would really like that option, more though I would love to be able to tell a romanced Astarion that he saved my life though, I mean, I can tell Mystra. But those are points on my list of very niche requests. XD
