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. 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)
Otherwise, he can use Sturdy Stance or another defensive seal to complete his kit. Finally, If Quick Riposte is not used in his B slot, it should be used in his Sacred Seal slot, as he’ll be hard pressed to perform follow-up Attacks without it due to his low Speed. For Mustafa’s C slot, Attack Smoke allows him to tank even more damage due to its Attack debuff against foes within 2 spaces, although his C slot choice depends on the team he’s in.On a budget, he can also use Quick Riposte for guaranteed follow-ups on Enemy Phase. It also gives him some extra damage output due to it’s defense debuff. Lull Atk/Def makes Mustafa even more difficult to take down, due to it nullifying the foe’s Attack buffs and reducing their attack by 3.On a Budget, Sturdy Stance 2 can also be used for a boost to Mustafa’s Attack and Defense. Sturdy Stance 3 can also be used to grant Mustafa a +6 increase to his Attack and Defense in addition to the Guard effect, making him more resistant to Enemy Specials. Distant Foil is a great skill for Physically defensive units, as it allows them to counterattack daggers and bows while increasing their Attack and Defense against melee opponents.Mustafa can also elect to take greater advantage of his fantastic Defense and specialize in countering physical foes with a Defense refined Rearguard or Slaying Axe.Sacred Seal: Quick Riposte / Sturdy Stance Passive A: Distant Foil / Sturdy Stance 3 / Sturdy Stance 2 Weapon: Rearguard+ (+Def) / Slaying Axe+ (+Def) Finally, defensive sacred seals such as Mirror Stance and Distant Def round out his kit and boost his defensive prowess further.Pulse Smoke is ideal to additionally grant Mustasfa the ability to circumvent dangerous enemy Specials by increasing their cooldown by 1 after combat, but his C slot is mainly up to player preference.When coupled with Null C Disrupt, Mustafa can also serve as a solid counter to Firesweep users and Healers, although Quick Riposte can be used in his B slot on a budget to guarantee his follow-up Attacks on Enemy Phase. Distant Counter is invaluable to Mustafa, as it allows him to counterattack a plethora of dangerous ranged threats that would otherwise be able to attack him without fear.
Bonfire is a reasonable alternative if one desires a pure damage special, however, as it scales extremely well thanks to Mustafa’s high Defense.