amazingchestahead: Are you playing the old version of the original game? Not The Original Saga?
If you enter the Undercity, or if enter the Temple of Bhaal, the game checks if the variable MissionPackSave is still 0. If it is, it will teleport you to Ulgoth's Beard.
In The Original Saga, this variable is supposed to be set to 1 if you enter the Maze under the Thieves Guild. Meaning that once you enter the Maze, the game will never teleport you to Ulgoth's Beard. Also in The Original Saga, the "teleport" action only happens once - if you return to these areas, it won't happen again. Try teleporting back to the Maze or Undercity after you have been teleported. See if it happens again.
I can't say anything about the pre-Original Saga version. If you see a MConverter.exe in the game folder, you could try running it. It converts your save to a save compatible for the addition of TotSC. I don't know if this helps though.
Back to your original problem - this is probably going to be full of spoilers if you haven't played the game before, but:
Normally (as in, no mods involved) Sarevok won't appear at the final area unless he has been forced to retreat during the ducal palace event. He says a line just before he runs away and this line sets SarevokBehavior = 1 which triggers his appearance in the final area.
As for the entrance door to the maze in the Thieves' Guild, it won't be open unless DukeThanks = 1, which is set when Belt or Liia urges you to go hunt Sarevok down at the end of the ducal palace event. This dialog, in turn, is also triggered by SarevokBehavior = 1.
What I'm saying is, if there's nothing abnormal, you need the coronation event to happen before just about everything else can happen.
Honestly I don't see how the event is not triggering if you've been playing the game normally without mods. But maybe these conditions are different in non-Original Saga version? I doubt this, but it's a possibility.
Try entering this line into the console:
CLUAConsole:SetGlobal("SarevokBehavior","GLOBAL",0)
This is the only variable that can POSSIBLY be different, since "Chapter" HAS to be 7, and Sarevok CAN'T be dead. If this doesn't work, then the ducal palace area in your game is, somehow, calling some other variables. Try this and see if the ducal palaces spawns all the NPCs.
OR, if you want to just skip the coronation altogether, try these lines:
CLUAConsole:SetGlobal("SarevokBehavior","GLOBAL",1)
(This forces Sarevok to spawn in the final area)
CLUAConsole:SetGlobal("MissionPackSave","GLOBAL",1)
(This prevents the game from teleporting you to Ulgoth's Beard. If it's not happening then you won't need this)
After this you can just teleport to the Maze or the Undercity. You can teleport to the final area if you want, but your party will spawn at the top corner of the area and that will kinda mess up the fight a bit.
Thanks for your reply amazingchestahead! Actually, I went full old school and installed windows 98 on my old pentium 4 machine, installed the game with the original CDs, and never modified it in any way. Maybe I should have patched the game to the latest TOTSC patch...
I tried all of your suggestions, both trying to set sarevok behavior to 0 right before I entered the palace and after entering it, nothing worked. I also put my file in MConverter.exe, tried to set mission pack save to 1, tried teleporting back to the maze after being teleported to UB, but nothing will do, I'm in a loop where I get teleported there over and over again... Same thing when I teleport straight to the temple.