Nephenee

THIS. This is my favorite creation. Nephenee's incredible speed allows her to run an incredibly mean Firesweep Lance+ build. The nature is +spd -res, as this increases her speed to 38 with pretty much no cost, as there is almost no magic those extra 3 res could save Nephenee from. Swift Sparrow pushes her offenses to 50/46, which almost always guarantees doubles in engagements, while also retaining the bulk which makes her so amazing. The Drive Atk 2 as the C skill is meant for a more team based passive and grants a slightly higher arena score. However, Threaten Def 3 offers a more unit-based, cheaper alternative that is still useful. Rally Def/Res is incredibly useful for your team and grants a higher arena score. The best part about this is that if you can pull a Roderick for a Firesweep Lance+, you can inherit this skill onto Nephenee as well, as long as you have either Rally Def or Rally Res on her already.

Now, the choice of B slot will end up effecting your special and seal, so this is an important decision.There are two main options you can go with, which are either wrath 3 or drag back. Wrath 3 is the least expensive, but requires the quickened pulse seal to pull off effectively. By combining QP and moonbow, Nephenee will almost always be activating moonbow in her first engagement. This, combined with + 10 damage boost from Wrath 3, and prior damage, will usually be enough to ORKO most enemies Nephenee goes up against. Notable kills while unmerged are:
Steady Stance 3, Lv. 40+1 Black Knight with Fortify Armor
Fury 3, Lv. 40+1 Xander with 2 Ward Cavalry's
Steady Breath, Lv. 40+7 +Def A!Tiki with Fortify Dragons
Close Def 3, Lv. 40+10 Neutral Sigurd with Fortify Cavalry
Steady Breath, Lv. 40+7 Neutral Nowi
Fortress Def 3, Lv 40+2 +Def Brave Lucina
However, if you want a more traditional Firesweep user that helps to support the team more, you can just run the standard Drag Back. When running Drag Back, you should run Bonfire and Atk+3 Seal, to make up for the lack of a damage spike as intense as the last one. While I personally don't recommend the Drag Back version of this build, it does have the advantage of being slightly more consistent than the QP + moonbow set.

One of the best team mates for Nephenee is Inigo with TA3 + Gronnraven+, as he can safely bait and kill both Reinhardt and Bow Lyn, which are two of the most meta-central characters in the game, as well as two of the biggest threats to Nephenee, although this is moreso for Reinhardt than Lyn. He can also help to take care of physically tanky blue units, which Nephenee tends to have trouble with. Another great teammate for Nephenee is a strong red tome user, such as Arvis or Celica, as they can deal with strong physical walls such as Hector and Zephiel that Nephenee has trouble finishing off. Keep in mind units like Arvis and Celica are almost mandatory with the Drag Back variant, as Nephenee will get many less ORKOs, but it will be easier for said mages to finish of her foes.

Build Name: Truly Fierce

Nephenee has great Attack and Speed stats along with good defense. This build focuses on Nephenee's Wrath along with her Slaying Lance+.

You want to run either an Attack or Speed boon on her. More attack is more damage, and higher speed allows her to double more and get doubled less. The bane should preferably be her HP, so you can proc Wrath faster. A Resistance bane will work as well.

Her set weapon is great. At 14 Mt and special trigger acceleration, the Slaying Lance+ is useful to help proc her special faster alongside Wrath.

Her support skill is interchangeable. Pivot and Swap are good for switching in front of physical attackers and protecting squishier allies. Ardent Sacrifice and Reciprocal Aid can also be used to help reach the <75% threshold to activate Wrath.

Ignis/Bonfire make uses of her good Defense stat. However, her set Moonbow is also a great special if you are on a budget.

Fury 3 boosts Nephenees stats, and although the health loss may seem less than ideal it will payoff when used in combination with Wrath 3.

Her Passive C is interchangeable. Recommended C Passives are Threaten Attack and Savage Blow. Threaten Attack helps Nephenee tank hits better. While Savage Blow can help when Nephenee is bombarded by enemies by inflicting additional AOE damage (and it suits the build's theme).

This is just a very very defensive nephenne who can take all physical hits well, and deal major hits back, while with fury making wrath usable, and procing Ignis easily.

The Durable Slayer
A build meant to increase her survivability. The noontime and wrath combo can heal her quite effectively thanks to the reduced cooldown her special will have due to the slaying lance. Fury rounds up her stats nicely will safely bringing her into wrath's hp threshold. Threaten def can be opted for pure damage potential, though it can be changed for a team buff; the same goes for the support skill.
It should be noted that she is switching damage for survivability, therefore a dancer is particularly useful to have her deal damage more consistently.

If you want the extra attack and +1 def you can use steady stance 3. Add 1 to def (only when she is attacked) and add 3 to ATK. The stats are with the passives already applied. This is a defensive Nephenee. I've noticed that against even named red melee units at level 40 they can barely damage her if they even can do anything to her same with blue units and green melee units can do 7-14 damage (A level 40 Fredrick did 7 damage) The Threaten ATK 3 is to reduce the potential damage even further. The weakness is most Magic users can put her in a bad spot. With the extra defense ignis does more damage total about 30-70 damage which she can proc almost every turn.