I'm playing a "let the chips fall where they may" monk Durge, because I can't commit to being evil but wanted to see what happens when I make different choices from my usuals. I'm not actively committing evil, so was resisting killing Isobel, but I let Shadowheart kill Aylin, not knowing that it would cause Last Light to fall anyway.
So now -- no Jaheira, no Minsc (except as an antagonist), no Dammon, no Barcus or Wulbren, no tieflings. Larroakan just kicked me out without a fight or nothing. All a pretty high cost to letting Shart go DJ, which to be honest is not much of a power up (although it's also possible I just don't know how to play with her effectively).
Not a complaint, I did the deed and it had consequences. But I won't be letting Aylin die again, so if this is the game trying to teach me a moral lesson, it worked.
You can still fight Lorroakan on that path. He tells you to leave, but there's nothing stopping you from giving him a Sussur dagger to the ribs instead. It would be a shame to let that loot go to waste.