I have and I am actually just about to break it out again for a party I started off with N4: Treasure Hunt using AD&D. They are exploring the islands and this will be one of the larger. To say I didn't add or modify things would be untruthful, though. I do that with every sourcebook though.
I'm starting to flesh out the Isle for my own use, so I'll dump some ideas here for sharing if you don't mind.
It'll be more or less "by the book":
The isle will be located in a pseudo-European medieval fantasy setting (likely using OD&D/WB:FMAG). The current "Young Kingdom" of the isle is built on an "Old Kingdom" of warlords, which in turn was built upon the dead remnants of "Atlantis". This means there will be plenty of ruins everywhere.
Towns, city, and geographical features will have a quasi-French flair to the naming conventions since (for me at least) the setting invokes a combination of Clark Ashton Smith's Averoigne, peppered with some Dunsany and Malory. The island map was inspired by the actual French isle of Corsica, so I flipped, rotated, and stretched the IotU map and laid it transparently over a real-world map of Corsica. From this, I associated actual Corsican town names with those on the IotU map.
There will be a monotheistic, "Lawful" religion, a few demonic/diabolic cults, and several mysterious cults dedicated to the "Old Gods" (a Greco-Roman pantheon, with a smattering of Egyptian myth).
Character classes and races will be BTB (O)D&D.
The Zodiac mages will be major NPC's/powers on the Isle, but I haven't worked out their true purpose yet.
I will be using undead and other traditional D&D creatures on the Isle, but mostly as one-off uniques in dungeon settings; the Chimeric beasts will be used as-is.
I'm toying with the idea of an island-central mega-dungeon in the vein of unpublished CG. The upper levels are the maddening laboratories of a long-gone sorcerer who was studying the magics of the Isle, the middle levels will encroach upon the haunted crypts and such of the ancient Atlanteans, and the lower levels will be where the Atlanteans forged their own doom in the ruins of a still-older civilization (this will be where the Isle's crazy monsters come from).
Last Edit: Jan 2, 2017 4:16:53 GMT -6 by foxroe: forgot some stuff