So, the PCs figured that they'd go to Furyondy and ask them for help since they were willing to mobilize an entire army to defeat the temple last time. The only way for the adventure to continue on track was for me to make everyone they talked to treat the entire thing as a joke, demand real proof and deny any proof the PCs came up with.
That's why I set the campaign during the Greyhawk Wars; with Iuz on their doorstep, they couldn't lend much aid. (Plus the added benefit of having refugees all over the place for their slavers to round up as sacrifices, which was a big plot point in my game.) I did have the Cathedral of Trithereon in Verbobonc give the PCs a Staff of Life with 7 or so charges in it.
As for the Mines, I found there was very little reason for the PCs to do anything but fight. It's possible that they could try some intrigue and convince one side to attack another...but given the information the PCs have when they get here, it's extremely unlikely. I mean, what they know is that there's a huge base of the cult in a mountain and that they are likely trying to bring back Tharizdun which will destroy the world.
The players in my game were able to turn the cultists against each other pretty easily. They knew (because Burne cast Dominate Person on Dunrat, and had tons of information early on - not a bad thing for the game, really) what was going on and how to turn the Temples against each other. What's more, the Temples are all CE - they're already at each other's throats. It doesn't take much to set off that powder keg.
The PCs took the cultist's robes from the moathouse, came up with a story that Naquent was trying to set up her own temple to steal power from Hedrack and the rest, and they were sent to the CRM to deal with her. They bumbled and pissed off the Water Temple, starting a massive fight; that brought the Fire Temple into the action (Kelashien figured that the PCs were working for Tessimon - who else? - so she did her assault, as in the module), and the PCs allied with Fire. When Naquent showed up, the PCs killed her, then killed Tessimon right away.
Hedrack was watching so he came by to see what was up; a lucky Bluff check saw a couple of PCs dragged off to be his new assistants (lucky because they could have been killed right there). They got even luckier when Hedrack had Satau read their minds to see what they wanted. (Satau did not ask the right questions - he never suspected that the PCs might be Good. The dice were with the PCs that night.)
Then those two PCs killed Hedrack (some nice tricks and I did not notice that he had a scroll of True Seeing, but them's the breaks), used a Hat of Disguise to take his place, and WON. (It helped that Rary and Robilar came by a couple of weeks later on to wipe out the rest of the Temple, thanks to the PC's actions in Greyhawk City.)
Though they nearly avoided a TPK in the final assault against the Triad.
*
The way I set it up, each Temple in the CRM was sacrificing slaves. The slaves were collected in Rastor and picked up by individual Temples. Hedrack paid for the whole thing, including supplies, by casting Greater Planar Ally each month and having a demon (Nalfeshnee? Glabrezu? Glabrezu.) use a Wish to give him 25k GP. (If the PCs were able to call and kill that demon, it would really screw up their plans - so worth a crapload of XP.) Naquent was the one who delivered the weekly payments and collected the souls - in the form of those balls and cones of incense - and Hedrack would use his Tentacle Rod to enter the Black Spike and drop off the incense.
The Triad was holed up in the Greater Temple at the top of the Black Spike, making an artefact that would allow Tharizdun to return (the Orb of Silver Death). (I guess they were using Zuggtymoy's imprisoned soul to help somehow, too.) The rest of the Doomdreamers were in the Sea of Dust, looking for the Bringer of Doom, which was a representation in the Material Plane of Tharizdun's prison. When opened, if the planes were properly aligned, Tharizdun would be released from his prison and cause another Cataclysm, just like the one that destroyed the Baklunish Empire.
Lareth's role in all of this was that he was specially-bred to be able to access Tovag Baragu, which I decided was "here and not-here", some kind of out-of-space-and-time deal. The Codex of Infinite Planes was at Tovag Baragu - though not "there" if you went and poked around, but Lareth could bring you to the Tovag Baragu that held the Codex.
When reading from the Codex, the planes would align, and only then would opening the Bringer of Doom actually release Tharizdun. And even then, just for a moment, so failure was an option, just bad - I figured they'd wipe out the middle of the continent, so Furyondy, Veluna, etc. If the cult accomplished this, they could threaten another Cataclysm, holding Oerth captive, and rule.
(I decided that the Codex caused the Rain of Colourless Fire. It was cast from the Codex by the Baklunish Padishah in a pre-emptive strike against the Suel, because the Baklunish diviners foretold that their doom was imminent. I read one of those interviews with Gary Gygax who said that the Elder Elemental Eye had corrupted a Baklunish god somehow and was partly responsible for the Twin Cataclysms, which was kind of a nice fit.)
My other issue during this time is that it caused the prime example of the 15MAD. They walked in, defeated 2 encounters then ran. I tried to create some urgency in the adventure by pointing out if they didn't move quick enough that it meant the end of the world. However, that didn't appear to work on them at all. They asked the same question: "Do we know how long this ritual will take?" I kept saying "No, you don't, it could be any day now" and they responded with "Oh...DAYS...well, then we won't worry about how long it will take."
I actually made a timeline for them based on the sacrifice schedule. I went through the module and worked out how long it "should" take, assuming 4 balanced encounters per day, when they'd level up and what level they should be, travel times, when they'd get teleport, a trip to Verbobonc to shop, etc. Then I added that many days (around three months) to the start date - early Patchwall in 583 CY.
I then gave a GP value to the Orb of Silver Death; then I took the "value" of a sacrifice in XP and GP for making magic items from the Book of Vile Darkness, and figured out how many sacrifices they needed to make in order to pay for the Orb. Then I figured out how much manpower they had (based on the CRM reinforcement guidelines in the module), how much a slave was "worth", and how long it would take a group of slavers to kidnap someone (based on the Profession skill) and return. I also had the Slave Lords of Suderham (from the Slavers modules) delivering slaves every six weeks.
The sacrifices required was in the thousands. So I knew when they started gathering sacrifices. I knew how many sacrifices were coming into Rastor, and how much taking them out would force the big-wigs to deal with the PCs - meaning that the PCs needed to be high enough level to deal with them, or the most obvious method of dealing with the cult wasn't as good as blindly hacking and slashing their way through - and from that I was able to work out how much XP the PCs would get for freeing sacrifices, killing slavers, destroying temples, taking away their cash flow, etc.
That was a pretty fun night, actually, working all that out and reading up on Greyhawk lore. (Canonfire and Maldin's Greyhawk were the two best sources.)
Though my math was off, it worked out well. The players felt the time pressure and were always on a go-go-go schedule. The big thing I didn't account for was Burne, who gave them access to Teleport much earlier than anticipated, cutting off weeks, if not a full month, from the schedule. Oh well, that extra time allowed the PCs to get involved in Greyhawk a little more. (A simple PC-on-PC theft led to the PCs uncovering Rary & Robliar's plan to wipe out the Circle of Eight! Another fun couple of nights.)
