The Mod consist of several main conceptions, i only write about which ones are actually present atm. 100% based on ModHooks and will not work without it.

Armor and mDef rework.
When armored actor is hit, 50% of damage applies to armor, and 50% applies to their hp. Damage to hp then is reduced by damage reduction, granted by armor. Armor grants more damage reduction than in vanilla.
Armor applies penalty to Defenses equal to penalty to stamina.
Battleforged and Nimble perks are changed.
Some weapons have Armor Penetration, this is flat amount of DR that will be ignored when this weapon hits someone wearing armor.
Some weapons have Armor Bypass stat, this is % amount of DR that will be ignored.
HP rolls on level ups are increased to 3-5.

Counterattacks.
All actor have 25% chance to counterattack. Counterattacks happens only if attacker missed or hit, but damage dealt to HP is less than 10%.

Simplifying and reworking combat skills.
It is not secret that AI is dumb and Player, even if their bros are weaker, still faceroll every Ai party just because Player utilizes combat skills for maximum effect and AI don't. I wanted to combine some special combat skills into basic attacks.

Blocking with Shield.
Shields instead grants chance to block attacks instead of granting mDef and rDef. This chance to block is not affected by armor penalties.
First rolls chance to dodge, if it fails, then rolls chance to block, if it fails attack hits.

Damage is reduced dependent on chance to hit.
It scales dependent on overall chance to hit, that affected by Defenses and Chance to block. Attacks with <25% chance to hit deal only 50% of damage. Attacks between 25%-75% chance to hit deal 50%-100% scaled damage, and attacks with >75% chance to hit deal 100% of damage. Described as 'effectiveness' in combat log.

Critical strikes.
There is 25% basic chance to deal 25% more damage. Some attacks have additional effects on critical strikes.

Backgrounds buffs.
Sellsword and Militia have scaled bonus to mAtk and rAtk. Militia can get up to +8 and Sellsword can get up to +14 if their mAtk and rAtk are equal. Bonuses are reduced by difference between mAtk and rAtk stats.
Hedgeknight has 15% more melee damage, stamina and hp.
Swordmaster have more chance to counterattack and more critical strike chance.

I also slightly changed some perks:
Reach advantage instead grants flat damage bonus dependent on base mDef or weight of armor.
Bullseye instead grants critical strike chance.
Anticipation instead grants massive stacking rDef bonus after being attacked by ranged weapons. It saves from damage bursts, but does nothing against first ranged attack every turn.
Duelist instead grants armor bypass while 'double grip' is active.

Changelog:
9 22 21
Buffed swordmaster background. Slightly improved text(that was left after debugging lol)
Fixed named items tooltip.
9 15 21 again
Fixed reach advantage. Added optional difficulty file(it does what Adam's 18 bros does + fixes minimal and maximum scaling at 21 bros).
9 15 21
Fixed rounding error when calculating armor bypass..
Fixed alps. Changed unholds to have more hp but less regen, their regen is reduced if they are poisoned or bleeding, removed hold out perk(they were impossible to kill with lone wolf).
Changed reach advantage. Changed duelist.
Fixed named weapons. Now they have bonus bypass and pierce if they rolled vanilla penetration. They have bonus crit chance if they rolled armor damage.
Defenses now cannot be modified below zero.
Something else i don't remember.
9 11 21
Changed 1h swords, hammers, bows, crossbows, daggers.
Changed bullseye to grant crits.
Fixed some bugs(impale bug and wrong damage calculation bug).
Added images.
Something else i don't remember.