After siding with Brega, we went to the Guild and killed averybody, and were unable to open the sealed door. (I'd been using this very room as my stronghold in Chapter 3, but was unable to access the Shadow Thief Cellar Key I'd stored here because of the map change.) We went up to the 2nd floor to find it totally empty of Thieves. The Amnish Centurion said to search the place for the key, which we did (due to the long-standing bug, 2 of the chests can only be opened via a Knock spell), but found none.
Okay, hmm... did you kill Larell or Renal (whoever was there) prior to trying this? The key spawns on them, but if they're dead... yeh. I'm guessing that might be what you've run into.
No--my order of operations was this: Get back from Underdark, get accosted by a Messenger who asked us to go see Brega, kill a few Githyanki, decant my Bag of Holding into the various containers of the 1st floor of the Guild, sell off what remained, run off to Brega, accept his quest, come back and massacre. Now,
before I go see Brega, Renal's old guards and Larell are hanging out on the 2nd floor.
After returning from Brega, the 2nd floor is completely abandoned.
Giving the key to the current head of that branch of the Guild (be that Renal or Larell) is a good thing, but only if you also remember to
spawn that head into the new area after the map change.
Oh--correction to my previous post: It was in Chapter 3 that we killed Mae'Var. And I forgot to add that Larell had nothing to say to us, ever. He just kept turning around to always be facing whatever party member was nearest to him, as if he was almost, but not quite, initiating conversation. This makes me think that he was essentially fake-talking himself, which is why he could never go Hostile.
So you betrayed Renal, killed Mae'Var, then went to speak to Larell? For lack of a better solution, killing Mae'Var when Larell's in power should really spawn STDEATH I guess, since it's the equivalent of killing Renal when you've done his quest.
The only time I killed Renal and saw Larell was on a pure bugtesting run: "I then Saved, and attacked Renal to test his difficulty, getting around Arkanis Gath by Ctrl-Qing and booting him." This is not the sort of thing that you leave as part of your game (since it means you just screwed yourself out of a legal way to get to Spellhold), this is the sort of thing that you try just to see what happens, and then Reload afterwards.
Which I did.
So, a refresher: In Chapter 3, I sided with Aran, accepted Renal's quest, killed Mae'Var, got the reward from Renal, and did all of Aran's quests. Larell never appeared, nor was he even mentioned. No further Shadow Thief activities of interest.
In Chapter 6, the events that I noted in my "Some new bugs to report" post transpired.
[ADD:] New bug: If you kill Aran before you answer the summons to go see Brega, Brega has apparently lost all memory of the job he wanted you do do in the first place. I think a "We have already done this" conversation thread is in order here, perhaps with a slight penalty to the gold, EXP or possible items you
would have gotten as a reward if you had been acting in a more official capacity.
On the Shadow Thieves turning hostile: I don't like the way that I practically have to Fail a Pickpocket on all of them to get them to fight back, but I do like the way that Marina (the Black Market Thief that's "adapted" via Rogue Rebalancing) can be kept alive and friendly even after you've killed everyone else, simply because I think it's so darn handy to have your own personal store right inside the front door of your stronghold.
Not even bad Pickpocketing is enough to turn Larell hostile, although I have found what does: Going into Stealth or Invisibility long enough for him to forget who he was talking to, then attacking him. May require multiple iterations.