When does this thing even work? I only managed to imprint some spells from human casters, anything else fails miserably, and not in a failed saving throw kinda way. The target has the spell icon, but no extra spells for me. Forget about a wizard skeleton or a Lagufaeth that is clearly using spells. 

 

Same with spell reflexion, not once have I seen it work. And I have been hit by a thousand Necrotic Lances. Can It reflect AOE? Does your perception counts for the reflexion hit? Is it a 100% chance to hit if you reflect it? Can you crit with a reflected spell?

`No idea about the imprint but if the reflection works like the shield it doesn't reflect Aoes and beam spells.

Reflection does work on beam spells like Ray of Fire actually, though it does seem to eat up charges per hit (the Ray also remains on your mage, by the way). What it doesn't work on is indeed AOE effects, stuff like Cackling Bolt and Rolling Flame, and anything that isn't a spell (like Cipher Powers, spell-like abilities like Prestidigitator's Missiles). It does work on non-damaging spells as well, by the way (like Halt).

 

In practice, when your wizard gets hit by a spell that qualifies, this triggers a Will attack on the originating caster. If this attack misses your Wizard gets hit as normal, if it at least grazes your Wizard doesn't get hit. Instead, the originating cast will roll to attack himself (so it can be reflected and miss). 

 

One thing to keep in mind with Skeletal Wizards is that (somewhat counterintuitively) they're not casting spells (they're spell-like abilities). I'd have to check, but presumably the same applies to Lagufaeth as well. This is also why Grimoire Imprint doesn't give you anything, the target has no spells to give you (the effect icon stays on them until it runs out regardless though; the effect is applied, it just happen to not do anything). 

You can steal spells from Ogre Druids and most human casters (druid/priest/wizard). Those are the ones I had success with.