If any of you have already played through it, I'm curious to know how your pcs ended up getting in; obviously a frontal assault is suicide, so that leaves the wyvern/deathweb caves. However, that approach would make it VERY easy to miss the black tower, among other things. Any thoughts/experiences?
My PCs made an alliance with rebels among the giants, helped assassinate recalcitrant giantish leaders, then made a raid inside via the deathweb caves to free some giant-elder hostages. They then regrouped, rallied the giants, and did a two-pronged attack--they came in through the deathweb caves again, while their giants came in from outside. The PCs killed the Headless Lord and the interior giants, then came out and fought giants and mammoths up above while the outside giants took out the harpies, jotunblood, ettins, and taigi giant.
Then Mokmurian arrived in force and there was a fierce fight between him and his hounds, and the PCs and a few giantish leaders. The PCs won this with some difficulty.
Later on, they found the trapdoor in the Black Tower and sent an invisible character down--who was noticed on a high Spot roll and narrowly escaped an area spell attack. She scampered up and reported what she'd seen, and the PCs quietly closed the trap door and told their giantish allies, "This place is cursed. Scram."
So there were quite a few things they never did, but I was pretty happy with the outcome. I thought it ran better than a solo attack on Jorgenfist by the PCs would have done.
The party should be 11th level, so an extended invisibility sphere would last 22 minutes. Coupled with teleport and/or dimension door (from scrolls, perhaps), that gets the party to or just inside Jorgenfist without alerting the rest of the stone giants.