A young Feral Beats Girl Matona and her friends have the option to have as an ally.
Ambi is able to use all the skills of the enemies you defeated (Including Percival's magic!)
Although talking right isn't this girls strength she makes up for it by being able to use every monster skill in the game. 
But the choice to add her to your party is completely up to you the player.

For Ambi's voice i'd like innocence but curious about the world around her.

Ambi is only 8 years of age. 

Her lines won't be many as she doesn't speak very much in the entire game.

The next few characters will only be a few npcs all the main major parts are added given a few small ones.

You meet her when she help you though a cave to the Castle to rescue Charlotte but you don't get the option to have her join you until a little later on.