Relatively simple, the damage types that occur in combat or otherwise.
For clarification, the Damage Scale.
Minor/Mild/Moderate/Heavy/Severe
Damage severity is subject to change based on material grades and levels between combatants
Physical Damage
Slashing: Hacking and Cutting applies to blade weapons, everything from minor scrapes, to severed limbs is under this category. Slashing is blocked by as low as ribbed leather, spesifically the metal reinforcement, but repeated blows could weaken the armor. Weapons 2 grades higher than armor negate the defense, armor 1 grade higher than the weapon negates weakening.
Impact: Blunt trauma, Pressure and Applied Shock Force applies to all weapons, everything from bruises to broken bones/shattered or crushed limbs falls into this category. Blunt weapons carry alot of impact force, bladed weapons, very little. Nothing actually blocks impact damage, flexible armors like leather and chainmail block none at all, but suffer no durability damage from it, shell armors like cracked leather and plate can be damaged or dented by impact damage, even cracked open if severe enough, but reduce impact damage considerably if it's not destroyed.
Piercing: Impaling force, basically, Minor piercing would only p***k the skin, where as severe would go through you, and keep on going. However for the sake of the level based lethality part of the roleplay, head, heart and vital shots dont apply as anything more than a critical blow.
Piercing is fairly reduced by as low as chainmail, the damage may pierce the armor, but at a fairly reduced severity 1:1 grade. Plate will deflect piercing unless the weapon grade is 2 greater than the armor.
Special Damage
Burning/Searing/Melting: Overall fire damage seperated into 3 categories.
Buring causes blisters and heat-rash type damage and is blocked well by as low as leather, chainmail is the only one rather ineffective at blocking it.
Searing causes scorched/charred skin, and instant scar type wounds, same armor resistance as burning, but can cause durability damage to leather, and metals to heat up.
Melting damage is actually hot enough to burn or melt away skin and tissue, leaving muscles and organs exposed, the depth of the damage is determined by the severity. Leather and chainmail is rather ineffective, as the damage will easily penetrate it, it can also melt weaker metals, and heat up stronger ones signifigantly.
Frost Damage: Cold like liquid nitrogen, This damage causes frostbite, frost burns. Heavy damage can make materials, even skin and limbs capable of shattering with a weapon. Frost damage can imobilize leather, making it brittle, but will block the damage from the wearer, metal armor provides little defense.
Electrical Damage: Truly Shocking, this covers static shock and electrocution . Most electrical damage will cause involuntary movement, stronger ones can cause numbness/paralysis, even unconsciousness. As the electrical damage gets more severe it may start causing heat damage, both internal and external. Electrical is blocked by leather, but metals may actually amplify the damage as they tend to heat when subjected to electricity.
Corosive Damage: Acids and Venoms, these usually cause tissue damage and material degridation. Minor might sting, possibly cause some necrotic tissue, Moderate would leave decent chemical burns, and Severe, would pretty much melt you to a pulp. leather's fairly effective at warding off acids, as well as shell armors, but chainmail, being porus doesnt really help. All armors will take durability damage if the corosive does as little as moderate damage to it with the defense modifier, below that it negates it.