As the title says, is there a decent build I can use for this pity breaker? I have a +atk -hp (32 hp) Innes with double fortress res, guard bow+ and quick riposte 2; and a +atk -hp Halloween Jakob without a build. Should I keep and build my Faye or just sacrifice her to my neutral IV's Bridal Cordelia for Firesweep Bow+?
I'd say fodder her to Bridelia. I feel that you'd get much more usage out of Firesweep Cordy as opposed to any Faye build, especially since you seem to have defensive archer options.
However, if you really want to make a completely defensive archer, you could build a Faye, even with the -res. Triple distant defense and a def/res based special will be pretty sufficient to tank pretty much everything, beyond what Innes and possible Jakob could do.
Well, since you're actually considering it, you may as well just fodder her off.
If you're asking from a straight-off objective point of you, this Faye is pretty sub-optimal. My first Faye had those exact same IVs, and I just ran her with Death Blow > Brash Assault > Desperation (most other archers can run this as well, or even better). Her saving grace is being a mixed ranged tank, but -Res doesn't allow her to tank as well unless you run her with Distant Def or Fortress Res (if you want her to tank magic).
Faye is just a tanky archer, with her triple Distant Defense build she becomes a ranged tank, regardless of her IV, you have a +atk so she will hit pretty hard. Only problem is that the triple DD requires a lot of investment from 5 star units, so you may not find it worth it.
On a side note, Close Counter, Close Defense, Quick Riposte Faye is also a pretty good build.
If you do decide to fodder her though, make sure you level her to 40 first for the catalog.
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