I would love to see an entire AP set in Osirion. I was thinking the Pillars of the Sun region, the Pyramid of An-Hepsu XI, and a boatload of gnoll barbarians sounds like a lot of fun.
There are some modules taking place there, so I guess that the chance of having an entire AP set there is very low. I think it might have been James Jacobs who stated that they would rather explore new areas of Golarion in the APs than revisit settings and areas already used in modules.
Desert Stuff for AD&D might be found in
- the Dark Sun setting, albeit with a different tone
- the Al-Qadim setting (great stuff anyway!)
- FR 3 Empires of the sands
- ER 10 Anauroch (both FR)
- I 3-5 Desert of Desolation (set in FR as well, but pretty generic)
- WGR 3 Rary the Traitor (Greyhawk)
- RA 3 Touch of Death (Ravenloft)
I´m sure that there are more, but if you can find the Al-Qadim stuff, you should be on a good way for arabian/desert adventures.
Stefan