I'm planning out a dungeon and I'm willing to take suggestions for room and encounters. I've designed an island fortress which was a former fey castle and has seemingly been scooped out of whatever plane the fey chill at and dropped into the middle of the sea. The fey are all gone all that remains are a set of keyed teleport gates that are out of use currently and some aimless will-o-wisps that float about the halls. The fortress, having been found by evil elves is now used as a prison, run by devils of all sorts, though none too difficult for a fresh party of level 10 adventurers.
What I've got so far:
~Pit of Despair in the former ballroom. Magically generated gateway used as a mental torture device to prisoners. With some good spellcraft rolls and defeating the guards the PCs can deactivate it.
~Unnatural high elevation swamp, staffed by myconids who harvest whatever crud they can to be processed into gruel. Probably full of fiendish nasty reptiles. also might be magically deactivated.
~the aforementioned teleport gates, long in disuse and only noticable by differently colored rings of cobblestones in the structure. with most light cut out of the place (for the benefit of the wraith prison guards, Azkaban-style) the adventurers may be the first people to spy these stones without the use of darkvision in ages. Naturally the keys are *pink heart, *yellow moon, *orange star, *green clover, *purple horseshoe, and *blue diamond. Each of these I'm hoping to make a magical item that is either in use by an occupant of the fortress or forgotten in a pile of rubbish/treasure. The yellow moon I want ot be a magical sickle used in a torture chamber. The blue diamond will be a crystal dagger. Pink heart is likely an amulet of health, but I'm open to suggestions on the others, as well as enchantments for the weapons.
The PCs' objective will be to enter however they may without dying and free a prisoner by way of navigating the teleport gates and snitching the keys from wherever they may be hiding. Any thoughts or suggestions are welcome.