Q. about item- Eye of Aiming

[PDF]

Eye of prec improves the wearer's prec by +5 (Eye is +8 but corresponding eye loss gives -3).
This increased prec is useful for anything that use Prec rating, ie missile wpns and non-100 prec spells.
Try it on an Anathemant Dragon and see the result !

[velk]

Why do you say use only with precision 100 spells?

Because if you use an artifact eye that has no precision bonus you get -3 to precision and have trouble hitting anything if you don't use precision 100 spells.