Somewhere around the 2 hour mark (maybe less; I spend a lot of extra time exploring everything), Lucile joins your party.
Lucile is special. She can learn almost any skill, magic, etc., whether used by monsters or by your own party members, simply by having the skill or magic spell used on her.
So while my two main party members both have Light and Shadow Jewels equipped (since I haven't found any Void Jewels yet), Lucile has no need for such things. :cheer: So I gave her a Thief Jewel (which I randomly got from an enemy drop, and which makes it so when an enemy drops an item at the end of battle, you get two of the item) and something else really awesome (can't remember what, and I don't have the game in front of me right now.)
But the Jewels are not what's important. This is:
Harvey or Amelia can use ANY magic spell or ANY skill in their arsenal, and if they cast it on Lucile she will automatically learn it (and consequently be able to use it in batttle.) Note the game does say there are a few exceptions, i.e. a few skills she CAN'T learn - but I haven't found any yet. Also, Lucile has a skill that makes the enemy more likely to target her, increasing the odds of learning enemy skills.
Why is this so awesome?
Well, in Eclipse of Illusion, one of the Job Classes let you learn enemy skills, and one of them (Guardian Force or something like that) was a HUGE defense buff - plus I believe there was a really powerful Healing skill as well, that you could ONLY learn from enemies.
So, I am going to go out on a limb, and suggest that there will be enemy skills in this game, that if Lucile learns them, will be ABSOLUTE GAME CHANGERS. (Plus a whole bunch that you'll probably never need, but probably spend a lot of time trying to learn anyway...)

Additionally - if one of your other party members has a really powerful skill that you wish you could use twice in battle - well, just go into a random encounter, use the skill on Lucile, and voila - you now have two party members who can both use the same awesome skill. (Example: Have Harvey use Ariel Slash on Lucile, then once learned, Harvey and Lucile can both use Ariel Slash in battle, in the same round even. This is a poor example because Ariel Slash is not that awesome, but I'm still at the early parts of the game so I don't have any awesome skills yet!)
IF - and this is a BIG IF - If Exe Create did this right, Lucile's ability to learn skills could prove to be an exciting and refreshing new twist on an otherwise familiar battle system. B)