Mustafa

Mustafa is a unit with surprisingly good bulk in res for an axe fighter, and as such, we want to take advantage of that, since that gives him an edge no other axe unit gets (the closest thing would be Hawkeye, but lacks a bit of physical defense, so mustafa feels to me like a better choice for this build)

This build benefits greatly from Groom hinata's weapon, the Huge Fan, because as long as this unit has a bonus, Mustafa will get the breath skills, helping him charge his special while he can keep his A slot free. Because of this, we'll run Rouse Atk/Res 3, it boosts our damage and bulk. (Having him as a solo unit makes him be less vulnerable to courtly candle conrad with lunge, since having him with a similar skill based around him being close to units would ruin the huge fan effect)

Aether is Mustafa's best choice, as it allows him to recover a lot of health, and huge fan helps him trigger it quite often thanks to being doubled. Mustafa also finds distant counter quite helpful, so, we give him distant ward to make sure he can counter magical units (distant counter would also work in case of a problems getting the skill, but ward's boost to res is quite helpful for a unit like mustafa, and he has already enough bulk to deal with daggers and bows, so not countering them isn't such a big deal). This is why huge fan is such a great weapon, as it gave us breath skill for free and allowed us to run a distant counter skill.

Lull Atk/Def 3 is quite helpful (I know in the B slot says Lull atk/def 2, but the unit builder of this web doesn't allow me to give him the upgraded version), as it allows him to survive a lot more hits and also shut down units that run boosts to atk or defense. And for the assist skill, I would recommend shove or smite. In general, I tend to prefer Smite, as it allows to push units further, increasing their movement quite a lot (specially helpful with Galeforce units), but Shove allows Mustafa to keep the rouse skill active when finishing their turn, and can also be helpful if you keep your support units close for a refresh, and also push them in case you need them somewhere else.

+10. All 5 dragonflower boosts, a spd boon and there. This man can reach over 40 speed during the fight by himself, without anyone else.
First of all slaying axe with a spd refine. It is nice to boost his own good speed more.
Pivot? Just take any skill here, really.
Ruptured sky? Thats a good skill for arena ranking and if you don't have kestrel stance 3 you can give him fury 4, we both know who has both ruptured sky and fury 4.
Kestrel stance 3 or fury 4 will boost his spd to above 40. Which makes it nice.
Repel 3? Yes. It works. With his already good bulk he gets even more bulky. At the cost of no speed loss
Joint drive spd? He needs e v e n m o r e s p e e d. We want him to compete with people that have actually good speed.
And finally, phantom speed combos with repel giving him about 50 spd for the counter on repel.

Yes. This build works.

This is a suppressor build for Mustafa. Legion's Axe+ (+Def) adds onto Mustafa's HP and Defense, and it has Panic Smoke on it, and Pulse Smoke alongside it will suppress foes' specials and stat buffs. Distant Ward is for countering against magic foes with added Attack and Resistance, and Null C-Disrupt is to block Firesweep weapons, Dazzling Staff, and other things. Quick Riposte is for a guaranteed counterattack, and Sol will help Mustafa restore HP for it.