Reading through this I didn't put all the pieces together, but "drow" really pulled it all together and made it something special. I would have liked some inkling as to how he managed to 'punish' people as he does, is it connections? Psychological manipulation? Drugs? D. All of the above?
I agree the end is cliche but that can always be changed as the DM desires. What really makes this a good piece as the setting and in many ways good settings are harder than good plots (good plots are always tailored to a group of players anyways). It is so well described and atmospheric, as well as able to be used in any swamp.
This device is the opposite principle of the Duke of Exeter's daughter, more commonly known as the rack, and was created for the Tower of London as the rack was too difficult to move up and down the stairs. Instead of stretching the body, the victim is forced into a compressed kneel and the clamp tightened.
The Breaking Wheel (Catherine's Wheel)
The victim is lashed upon a large wheel, with joints in paritcular places. They are then beaten with clubs, which combined with the pressure points of the spokes easily break bones and joints. The rubbery usless limbs are threaded through the spokes, and the wheel is placed up high for the victim to die of dehydration days later while being pecked at by birds. Mercy may be extended by strangulation of the victim after several blows, or a coup de grace.
A seventeenth-century chronicler wrote the victim looked like, "A sort of huge screaming puppet writhing in rivulets of blood, a puppet with four tentacles, like a sea monster, of raw, slimy and shapeless flesh mixed up with splinters of smashed bones."
I like the idea of this as a sort of treasure hunt, a way to encourage players to explore places more thoroughly than they otherwise would. The submission needs some polishing, some sentences don't read as clearly as they should and some words didn't get spell-checked (libaries, buchered). I think the backstory could be more detailed as to why they were so interested in secrets in the first place, but the core idea is solid.