A worm crawled into my ear and wouldn't go away so here it is: a relatively quick and dirty reskinning of D&D to fit into Earwa. Comments and so forth are more than welcome. Steal as much or as little as you wish to. Why D&D? It's not a great fit, but the mod is relatively easy to do and as I said, it won't go away.
First things first. It has to be Fifth edition because the bounded armor class and attack bonus system is the only one where having mostly mundane armour and weapons can actually work and hordes of low level monsters don't have to roll natural 20s to hit a mid or high level hero. Also, a few other details work out better. I'll get to them in time.
Races: Humans, of course. I'll cook up a take on Nonmen an when I can. Nonmen is going to be hard to do without being wildly unbalanced although sufficiently nasty Erratic penalties can offset that. . Dunyain are even more broken than Nonmen. Half Dunyain or a defective is still damn strong, but might be manageable. They make much better NPCs and they make Nonmen look common.
Classes:
Barbarian: Obviously in.
Paths
Super Berserker type: Holca. The super berserk badassery works better as a Barbarian path than as a racial trait. As for their brute power, I don't think that needs to be addressed other than "Holca NPCs tend to have lots of Barbarian levels and good Strength and Con." Sure they're huge and powerful, but so is Cnaiur and so is Yalgrotta Sranchammer.
General Badass: Thunyeri. Should incorporate the tidbit about Thunyeri bolstering their defences by keeping their enemies off balance with fierce strikes.
Horse Warrior: Scylvendi goodness. Or badness, depending.
Bard: Nope. I know, Bardic Priests, but they're non magic using priests, no spellslinging rogues.
Cleric: Nope. Yes there are miracle workers and Shamans, but they are so rare they make the Few look common . Shamans are holy sorcerers and miracle workers are vehicles for DM action. So no, not as a class that can be taken.
Druids: See cleric.
Fighter: Hell yes.
Monk: Nope. Yes, I know the Dunyain are monks but they aren't D&D monks with magic ki powers and kung fu more badass than broadswords.
Paladin: Nope.
Ranger: Use the nonmagic Ranger variant(s) that you like. There's a small army of them out there.
Rogue: Yes.
Sorcerer: Baseline class for users of the Psukhe. Some Surgery
Warlock: No. After all, damnation is nothing special in this universe. Why give out powers for that? You fall as fodder anyway.
Wizard: Baseline class for Schoolmen. Some Surgery.
Arcane Traditions: the specializations that exist already can work, but to have some that reflect the world of Earwa and the distinctive nature of its sorcery would be a shame. So:
Anagogic War Cant Master: the Evocation Specialist.
Mandati: This is tricky, because you want the Gnosis to be distinctive and powerful, but you don't want it to wreck all balance. So instead of the standard type of arcane specialist we have instead the following:
-Relive the Apocalypse: Upon every long rest must make a DC 8 Con save or recover one less hit die and be at -1 penalty to all dice rolls until the next long rest due to disturbed dreams.
-The Gnosis: All spells, where applicable, count as being cast with a spell slot one level higher than actually used.
Iswazi: This is going to be tricky. It's generally stronger than other anagogic sorcery but less flexible. D&D rules doesn't deal with this particular issue well because it doesn't really have group spellcasting and its baseline sorcery is fairly inflexible. I'll see if I can cook up more than "has to use material components"
Sorcerer: Puskhe user. There's been a few blind miracle workers before the Cisharaum so it can work for a non Fanim group.
Changes: Spell list is massacred. A lot of transformation spells are out, as are teleporting type spells, a lot of necromancy, and summoning. Spells are reskinned from D&D standard to have visual effects more closely match Earwa's magic. The sorcerer is vulnerable to Chorae and is blind, but can perceive the onta and see the Mark without difficulty as well as see through the eyes of a bonded animal. This is limited, giving the sorcerer the ability to see but making all vision based perception checks at Disadvantage if they don't involve magic.
On the plus side, no need for components at all, no Mark, and the Psukharim's spells are indistinguishable from the world and thus not detectable as magic. The Sorcerer has double the usual number of spell slots so the character more closely matches the ability to throw around a lot of magic evidenced by Earwa's spellcasters and to compensate them for the diminished variety of spells and the existence of Chorae.
Wizard: Similar to sorcerers. Demon summoning is allowed and the "too complicated" barrier on Psukhe doesn't exist. The difference between Gnostic and Anagogic magic is going to have to be mostly simulated by throwing levels at NPC Gnostic Schoolmen. PC Gnostic magicians will be less advanced in their mastery than equivalent level Anagogic PCs. Yes, less than ideal. Cooking up an Arcane Tradition for Anagogic and Gnostic practitioners, the Gnostic one focusing on brute spellpower and the Anagogic one probably focusing on the Daimos (which is, after all, actually capable of threatening a Gnostic Schoolman in the source material) will probably help but I'll actually have to look at 5th ed material to do it right so it will come later.
Also can see onta and the Mark, are Marked, and also vulnerable to chorae. Also suffer from ravaged spell lists and gain double the number of spell slots. Spells are reskinned so Fireball is Falling Suns or the Dragonhead, Lightning bolt is Nibelitic Lightning, etcetera depending on tradtion.
Gear
Armor
No Plate Armor as standard, available armor. Mail is common and mail reinforced by steel splints (aka splint mail) also shows up.
Nimil Plate does exist. Good luck finding it in your size.
Nimil: Armor is half weight, counts as one category lighter. +1 bonus to AC. Weapons +1 to hit and damage.
Chorae
Grants total immunity to the direct effects of magic. Attachable to missiles or useable as a melee attack. Both suffer a -1 penalty to hit. Totaly destroy wards on a hit or missing by one point, ignore magical protective effects. Any magic user hit suffers +2 hp of damage per spellcaster level. Yeah, not instant death on hit or save or die. D&D hit points are abstract and losing hp can mean a near miss that uses up the last bit of the Whore's favor before your skin is punctured. Ditto with Chorae hits.
Scourging the Earth: Any magical attack that can potentially cause serious damage to a Trinket bearer with secondary effects counts as Scourging the Earth. Burning horses, blasting the earth and sending stones flying, splinters of wood and stone all count. Chorae bearers suffer 1/2 damage from such spells (again, damage is abstract in D&D and they are protected from the primary effects) and gain a +1 to any relevant saving throws.
Billows: Can be animated with Unseen Servant (or equivalent). Only deployable in the air. Grants a +2 bonus to AC against ranged attacks.
Wire Screens: Limits Dex to max +2. Weight: 10lbs. +2 AC versus ranged attacks.