ToME: the Tales of Maj'Eyal

Daggers apparently get "% APR" from accuracy. Does this penetrate a X% of the target's armor, or does it add +x% to the dagger's base armor pen?
The printed crit chance for an equipped axe doesn't change when my accuracy does. Does that mean that the accuracy benefit is hidden and my real crit chance is higher than listed?
Staves, shields, and gloves grant +proc damage. As far as I can tell, this applies to bonus damage on the weapon itself as well as bonuses from other gear, like alchemist gloves. Are there any talents that are considered procs? Temporal Folding, or instance? Incinerating Blows? Vile Poisons?

from what i heard elsewhere.
accuracy bonus is a bonus to the mentioned stat based on the positive difference between your accuracy and target's defence.
so the more you have accuracy above the target deffence, the more apr (armor penetration) you have when attacking that target.

This is correct and is also the reason the accuracy bonus isn't displayed (it'd be different for every enemy you fought, though I suppose it could be shown on the mob mouseover).

I believe almost anything that can happen passively on an attack counts as a proc. Arcane combat's flame and lightning casts notably do, making staff AB capable of stacking some nice extra damage through accuracy, though earthen missiles doesn't (as it generates projectiles which don't get the bonus).

Is % APR a percent reduction in enemy armor or a % increase in your existing arpen?

arpen is arpen.
it increase your arpen by the resulting %, which you can't see.