|Fir becomes a potent force with her new weapon.
This build aims to leverage Nameless Blade on a budget by turning Fir into a close range duelist that can rely on fast Wo Dao activations in order to quickly output damage.
The ideal boon for Fir is +Atk, as it is a superboon patching up her base attack a more acceptable 29. Because you are running Fury 3, Fir will generally have more than enough resistance to ploy the targets that she needs to ploy. In addition, because you are focusing on melee matchups, and her resistance is already very high, -Res lets Fir have better times against otherwise marginal matchups.
Nameless Blade makes this build, as it allows Fir to patch up her abysmal attack by giving her a flat +10 damage every special attack, and giving her the minus cooldown effect so she can activate her special basically every combat.
Reposition is generically one of the strongest assist skill, allowing Fir to move her allies behind her so she can tank the hit and then activate a special against them. However, other assist skills also work fine.
Moonbow is the best special for her given its low cooldown to synergize with the damage boost from Nameless Blade. When baiting she will immediately activate the skill, and with Wrath 3 she will immediately have it up for the next combat. Moonbow performs slightly better than Glimmer due to the latter not scaling off of the flat damage increases and thus being less effective due to Fir's low base attack, but either can work well.
Fury 4 provides a cheap, effective way to increase Fir's bulk while also increasing her damage output. With it she can better duel melee units with only a small drawback.
Quick Riposte 2 allows Fir to better duel tanky bruiser units by allowing her to always double on her first combat. This is especially important because the boon and weapon choice leaves her without much extra speed, making her speed tier okay for avoiding getting doubled but almost never enough to double enemies back.
Guard 3 is also a very strong skill on Fir, letting her initiate freely on dragons and punishing armor units reliant on specials. Another choice for a B skill is Swordbreaker 3 or some other breaker. This allows Fir to diversify the threats she can check, but at the price of having slightly worse matchups overall.
Def Ploy 3 is a very solid C skill for Fir given her naturally high res. While it will not activate on res tanks, she will generally be able to OHKO them anyways due most mages having bad defense. This provides her with about 5 extra attack on enemies, in addition to letting her support her allies.
If that is too expensive, and Hone/Spur/Tactic also works well with her.
If Fir runs Quick Riposte 2 then Close Def 3 becomes the best seal for her. Due to not having access to Distant Counter it is best to shore up her melee matchups, which Close Def 3 is very adept at.
If Fir runs a breaker as her B, then Quick Riposte 3 becomes the best seal for her, as having a source to reliably double initiated upon is important.