Shemeska
Adventurer
Alzrius said:It isn't official, but there is also a fan-made Planescape web-novel called Fire and Dust by James Gardner.
Actually it might be official since it was actually bought and paid for by TSR as I recall, but it never saw print. The author since released it for free on the web.
Guide to Hell - this genericAD&D supplement details everything you wanted to know about Hell but were too afraid to ask...it even has the half-devil, something unseen in 2E (and maybe 1E as well) until then.
Warriors of Heaven - a generic AD&D supplement on how to use celestials as player-characters, and how to run a celestial campaign.
Lots of contention of these two precisely because they lack that Planescapey flavor and all. A ton of people reject GtH because of the direction it went with Asmodeus, but I'll stop at that or else I'll open up a can of worms.
WoH was interesting, but I thought it heresy that it gave non immortal life spans to many of the celestials. Art was good though.