- Mercenary: Available automatically from the start of Bandit Suppression, then appears in the Mercenary Guild.
- Permanent: Raise her Level to 10 or higher and her Happiness to 12 or higher (after completing Chapter 10, the Happiness requirement is 6 to unlock a scene with Faramir) to unlock her personal mission Raze Altar; complete it, and she will leave, then reappear and join permanently at the start of the next chapter.
Faye is, overall, a mediocre unit. Her one good starting stat is speed of 12, which allows immediate cut-through to enemy crossbowmen and hand axe pirates, but other than that her other starting parameters are low. While her sword skill growth is 90%, with a base of 4 it will take a while until it gets anywhere and with a 4 strength and 1 defense base, she is left quite vulnerable provided she fails to dodge. For training her, she has her PRF sword, the Cutlass and she relies on it to get going - so much so that it's worth using a repair stone on it once.
Her main purpose is being an offensive unit - with Adept and Critical she can put up some good damage and if you get her sword rank high enough, Parry will have a good rate of activation, however it will take a long time for her to reach her full potential. Her strength growth of 25% isn't bad per se, but with an abysmal base of 4 she'll be relying on it a lot. When she gets to promotion, she learns the Astra skill, which essentially allows her to eliminate an enemy every 7 turns, as well as the Blade skill, allowing her to use blades. However, this is all in the lategame - before that though she'll mostly be a liability when not using her personal sword, as she doesn't really have the survival skills of Kramer the immense offensive capabilities of Ouro and her extremely lacking bases don't do her favors.
It is worth noting that if you do permanently recruit her, she's forced in Endgame where she can obtain the Divine Sword Vritra which has 16 might, 8 precision and +18% crit, along with negating the effect of Chaos's Divine Sword Vajra. She can, however, still struggle to kill Chaos because of her reliance on her shakey strength growth - at base strength plus her promotion gains, she deals 1 damage per hit, 3 with the Giant's Brace equipped. If this is a problem in your mind and don't quite know how to handle Chaos otherwise (Dean with Wrath, Ouro with Deathmatch and Grimhild, etc), it might be worth to throw the Strength Potion her way just so she starts doing significant damage.
Overall she's very mediocre in the early game and good in the lategame (but not outstanding). With a couple of lucky procs / rigging from 5-turn-saves, she might become a good offensive machine but she'll be lacking in durability besides Parry, which will eat through her weapons. She will probably never reach Ouro in usefulness but she'll be easier and cheaper to recruit. Just like with almost all Berwick Saga units, use her if you like her, as at the end of the day there are no truly unusable units in the game.
- While it is never mentioned in-game, in Shouzou Kaga's notes, it is revealed that Chaos (real name Fana) is—or was at least planned to be—Faye's older twin sister.