and also Wyrm's rock fortress,
I'd been reading about that one, but it never happened to me before last night - which prompted a minor freak-out by Karlach afterward, because I hadn't planned on confronting Gortash at the point (I was simply trying to eliminate the ground level guards after taking care of Ansur). Made me feel like such a jerk towards Karlach, lol!
I'm not sure if this is what triggers it, but: I'm very sure I'd always started the whole Gortash thing by simply walking into the fort from either Wyrm's Crossing or from Lower City (mostly the former, IIRC). Which had always aggroed the guards at the gates and, eventually, the rest of the ones at ground level. But never did it aggro anyone above ground level, including Gortash. Which is precisely what happened last night when I entered the area by taking the stairs up from the Wyrmway/the prison into that Flaming Fist reception area.
The guards in the reception area triggered a separate fight (as expected), but then leaving the reception area and stepping into the main road aggroed nearly everyone in the whole building. Gortash and all the guards in the throne-room joined the fight immediately and arrived downstairs after a turn or two. The dude died right there too, but when I looted him and the cut-scene of Tav taking the Netherstone played, it was set inside his quarters - and *not* where Gortash's corpse was actually located. Which leads me to believe that this is, indeed, a bug/glitch and not an intended scenario.
This seems only to happen to the upstairs guards within the throne-room, BTW. The ones one floor further up (three in Gortash's private quarters, plus a random guard from just outside his quarters) were still there and only attacked/spotted me when I went up there to loot the place.
Writing about this now, I'm not even sure why Gortash was still lurking about the throne-room at this time. On most of my earlier play-throughs, he was a floor above that (in his quarters) at this point in the story. Which is also what he tells the party after the coronation - that he'll be waiting for them in his quarters upstairs from the throne-room. And that's where the fight usually happens, IIRC - although on at least one other run it did also trigger in the throne-room for me.
Weird.
S.