Hey, first post haha 
I’ve done a revision on the 3.5 system to fit some things from other systems (advantage/disadvantage, for instance). I also changed most of the character classes, and some athas.org’s prestige classes and feats.
It started as just an amalgamation of SRD + DS3, but it began to be much more than that. Now it’s mostly PHB + DMG + DS3 + Athasian Emporium, with many, many changes.
Here is the whole book, 400MB with revisions to races, classes, and much more.
Changes from d20 system include:
- Advantage/disadvantage
- New skill synergies
- New skill uses
- New feats (including those mixing two classes, e.g. fighter and gladiator)
- Fighter feat and skill feat categories
- Revision to psionics and some psionic feats
- Psionic tattoos are permanent
- Intelligent items are psionic
- No dorjes, psicrown, psionic weapons/armor, psionic constructs, universal items, or psionic stone.
- No arcane archer, blackguard, dragon disciple, duelist, dwarf defender, or eldritch knight.
- Crossbows function as composite bows (with Str rating)
- Metal weapons deal +1 damage
- Shields (not bucklers) have +1 AC
- Only one NPC class: Settler
- Different settlement categories
- New epic rules (still not finished)
The book was split into six low-resolution PDFs:
- Player’s Handbook (Races, Background, Archetypes, Classes, Skills, Feats)
- Athasian Emporium (Equipment, Magical Items)
- Universae Grimoire (Magic rules, Spells)
- The Will and the Way (Psionics rules, Powers)
- Wanderer’s Journal (Athas, organizations, planes, other ages)
- Dungeon Master’s Guide (everything else)
