I am new to planescape, I had stubled upon it quite accidentaly and was enthralled with its concept. HopefullyI am not being to forward, or at least excuse my ignorance, but are chapters 1, 8, 9 available to download
Thanks
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As you can see, i'm clueless too, but to my knowledge they have yet to be converted/updated from the old 2nd edition.
If you want some more stuff on planescape then you could buy some of the old modules via ebay or something (but they can be quite expensive as my wallet knows).
A very good idea (imo) would be to pick up a copy of Planescape: Torment for the PC (I'm biased here + probably only a good idea if you have some PC games exp). It is really good at conveying an immersive planescape atmosphere.