For me this one wasn't a huge challenge, mostly because I didn't get a chance to talk. I snuck around him a bit scouting out the place and freed a prisoner, after which all of the cultists went hostile and dialog was impossible. Jaheira was also on hand to remind me how the last fight went, so I saw reason for tongue wagging and ambushed the blackguard.
High levels in tabletop 5e are unbalanced according to what I've heard. I've only played in a single high level game that was a "one-shot" dungeon. The only reason we survived a lich and his undead army was because I shifted to the astral plane and blasted the MacGuffin from there with a few Prismatic Sprays. When it blew up, it took the lich with it.
The main reason I'm not a huge fan of high level games is because you often end up with too many options. Please see
decision fatigue.
