How do you access Marten's idol (and the ghost-filled area that occupies the eastern portion of the keep)? I had no problem getting inside the central area (where the squisher/elevator/etc are found), but the only apparent opening into the other section is a drawbridge-like door directly across from the squisher and I'm not sure whether that even opens from this side.

I remember having trouble with this back when Wiz8 first came out, but it's been so long that I don't remember what the solution was!

There's a catapult you can use around the right side of the keep from the entrance if you haven't used that yet.

You have to traverse your way through Lower Marten's Bluff to get to that area. Once you get to the central ghost-filled area on the upper floor, one of the switches will open the path to the idol.

bevinator is right about the mines... once you have done that then there is a trap-door you can unlock from below so that you don't have to do it again next time.

P.s.
You could take Saxx with you into these areas but I don't recommend it!

I used the catapult to get inside as soon as I arrived - that's one part I did remember! That gives access to the 'front' T'rang area (and the journal), but it sounds like the long way around through the mines is the only way to open up access to the idol. Ah well. Long slog, here I come!

(Edit: D'oh! It looks like I didn't check the "Question/Solution" box when I made the original post!)

You don't actually have to go through the mines. If you grab the T'Rang Arm from the dead guy next to the arrow trap on the top floor, you can access virtually all of Marten's Bluff, both upper and lower. (The arm opens the hand-scanner door in the room with Z'Ant.) The Mine Tunnels only give access to a relatively small area in the very back that isn't necessary to reach the Idol, but they're worth doing anyway because of the NPCs and items that live in the Tunnels themselves.

Well, I ended up taking the long route around and cleared out all of the loot.

I wasn't sure about using the arm to get into the rest of the area because while the tunnels do link up, you have to walk past some T'rang guards who get touchy about you being in the area, and turning the whole lot of them hostile would complicate the rest of the MQ a bit!

There's a way to exploit the game mechanics to get past them while keeping them friendly. Step into the room. When they give you a second warning, initiate combat. Since they're still friendly, it'll be your turn. Now simply use up your turn to run to the opposite doorway; you should have just enough movement points for that. End combat. Now you're on the other side, and they're still friendly to you. This area contains a teleporter to the area outside Arnika, which is very useful.

Yes, it is! (And there are a couple of nice items hiding out inside that building, too.) I thought the similar building outside of the monastery was also linked to that teleporter but I guess it actually comes from somewhere else.

I'd completely forgotten about the combat-dash trick, and that's something that ought to go into the "Things you wish you knew..." thread, because it's useful in a number of places.

Thanks for the pointers, everyone!

The second shack is linked to the Umpani teleporter. You'll meet them later if you still haven't. Each teleporter can teleport you to three places. Careful not to go to the area you're not prepared for, because not all teleports work both ways.

For the record, you can actually murder absolutely everyone you meet in 6+7+8 and still finish the games just fine. Killing Barlone' in 7 is tricky because you have to talk with him first and THEN piss off or kill Ratsputin, who is unlikely to still be alive at that point. And you have to wait until the finale of 8 to kill Bela a second time, because he can't be fought in the mountain wilderness.

But it is possible to play a group of murderhobos for all three games, which is one of the nice things about them.