So I may have painted myself into a bit of a corner here. A while ago in a home game that I run I introduced a tower that group of mercenaries called the Shadow Clan discovered. It is said that in times past that this tower served as a training ground and test of skill. Those who passed the tests were deemed worthy of becoming one of the renowned Shadow Masters (title only, not really a Prestige Class or anything).
The problem is that I brought this up back when the party was only level 6 or so. I had plans on what I was going to use for the tower. I was going to be running a modified Jacob's Tower and am still strongly considering purchasing it for other future uses. My party decided against pursuing that particular path at the time but ever since then has shown a deep desire in every one of them to go back and pursue that tower. The problem is that they have since long outgrown it. They will likely be 12th or 13th level before they have a chance to pursue other goals than the adventure they are currently on. That outright eliminates Jacob's Tower as an option.
I am also at a point in DMing where I am coming up with several original options for them at once to avoid railroading and am busy on the other paths they might take. I want something predesigned to use and modify for this tower and am coming up empty handed. I was hoping that some of the good experienced DMs of this board might be willing to offer some suggestions.
Here are my requirements:
1. When I say "tower" that is misleading. I want it to either be a barried tower that they have to go down into, or a series of sub-basements. There is another reason for this. The end of this campaign will lead them into the Underdark of my homebrew world and have them face some threats there. There are other important reasons as well like the fact that the party now has easy access to flight and there would seem to be no reason to not start at the top of the tower if it were above ground. Even with it being underground I suspect they are clever enough to burrow but that at least offers some difficulties to most of the party. I can wiggle around some of this and modify existing works to match this requirement well enough, I'm sure.
2. It needs to be big. Probably nothing close to mega-dungeon size. A full module would be nice though. Even a large one.
3. It needs to appeal to the rogueish types. Obstacle courses, labyrinths, traps, skulking, puzzles, etc are all valuable to this kind of thing. If the purpose of the place is to test the skills of a band of shadowy assassins then this seems important. The whole thing doesn't need to be this way. Maybe just some of the earlier levels.
4. Easily modifiable to fit the aforementioned points. Well, I would likely settle for modifiable.
Also, a little background on the campaign:
This campaign follows a group of adventurers who came under hire from a man that was later revealed to be a Steel Dragon. He brought them under his tutelage due to the rising dragon related activities in the area. The first part of the campaign started out with a modified version of Dragon's Demand. Many of the foes were made more dragony and the impetus of the BBEG's academic interests were not on the Dark Tapestry but rather on the Underdark. This was forshadowing but was never deeply pursued. At the end of this arch their former sensei revealed himself as the Steel Dragon he is during the destruction of Belhaim (modified from the original work) and this set off a chain of adventures revolving around the dealings of dragons as the movers and shakers of events happening around them.
They have also visited a modified Menagerie from Dragon's Unleashed. They explored a gnomish mine named Castengrove (original work of mine) that had been massacred by one of the Swarmlords. They very nearly stopped the sale of an ancient evil relic that is actually the egg of a Phoenix/White Dragon amalgam and sacred to a band of Ice Trolls known as the Stormborn. Sadly, the leader of this band escaped with this relic in hand. They have freed a swampland of a magical Blight, slain the Swarmlords and at least one of their masters and an evil Unseelie Fey Blighted Black Dragon. They have restored a World Tree in this same region and built a new Druid Caern that can be used as a teleportation circle linked to several other Caerns on this world. They have brought with them survivors from many of their past adventures (including survivors from Belhaim) and established a base of operations in Castengrove.
Their current adventure has them pursuing the Stormborn in the Frozen North and the relic/egg containing their deity. They have some other avenues they are likely to pursue after this. One of them is the tower I have mentioned. Another is a siege upon their base of operations while they are away that I plan on handling a lot like True Dragons of Absalom. The others I will be working on with original works. It is this tower that I need help with.
The above spoiler is really the long way of saying that this is a largely Dragon-based campaign where Dragons are the movers and shakers of their adventures. This will probably represent one way I would be modifying whatever module I decide to use.
Aw... no suggestions?
One more try for a bump on this. I have been looking and still haven't found anything particularly good for this.