Armor Penetration and attacks

As Wiki says: Armor Penetration (often abbreviated as AP) is the amount of armor that an attack or spell ignores when calculating damage.
In regards to attack skills though, aren't all attack skills armor-ignoring? That is, wouldn't skills like Power Attack or Death Blossom do its full damage? Since the damage of attack skills isn't affected by armor, what's the point of armor penetration on attacks? Does it only apply to the base damage of the weapon? If so, it wouldn't be helping much, would it?

// A sword does 15-22 damage, which is halved to 8-11 if you attack a 100 AL target of the same level. Tack on a skill like Judge's Insight, and you'd be attacking a 80 AL target with a range of 11-16. In this case, giving a sword user 20% armor penetration is only adding 3-5 damage, which does not seem like much, right?

I can only offer a partial answer.

There is a difference between an attack skill that deals +25 damage and an attack skill that deals 25 damage.

The first deals the weapon's basic damage (say 15-22) AND an additional +25 damage. The damage from the weapon itself is affected by armor and can in some cases get ridiculously low (HM warriors and so on). The bonus damage is armor ignoring.

So, the armor penetration only affects the part of the damage that is affected by armor.


Note that some other attack skills replace the weapon damage (for example, needling shot).

You're right attack skills' +...damage is armour-ignoring and AP only affects the base weapon damage. It can be useful depending on how much AP you have and the max weapon damage possible.

It depends on:
1. the skill used
2. the target's Armor Level
3. the weapon you're using

Example: Penetrating Attack (bow skill)
If Penetrating Attack hits, you strike for +5...21 damage and this attack has 10% armor penetration.

Some things will stack, others won't. Mods have an effect etc.

Check out the wikis for the math on attack bonuses.

Hope that helps