Flame Emperor

Weapon: Wo Gùn+ (+Res) / Huge Fan+ (+Res) 

Assist: Swap / flexible

Special: Noontime

IVs: +Res or +Atk / -Spd

Passive A: Distant Counter

Passive B: Special Fighter / Slick Fighter / Crafty Fighter / Vengeful Fighter

Passive C: Pulse Smoke / A/R Far Save / Armored Stride / flexible

Sacred Seal: Quick Riposte / Mystic Boost / Atk/Res Bond / Atk/Def Solo

• While Flame Emperor does not have a strong non-inheritable Weapon like some other armors, their high stats allow them to perform well as a tank in Aether Raids or other modes. 
• Pairing Wo Gùn+ with Special Fighter and Noontime allows Flame Emperor to get attacked and immediately retaliate with a Noontime that is boosted by 10 damage, so long as the enemy does not have a Special-slowing effect such as Guard. +Res is generally the most useful refine, since Flame Emperor’s base Resistance is much lower than Defense. 
• Huge Fan+ can be used to provide a Special acceleration effect so long as Flame Emperor is buffed, which is a fairly easy condition to meet, and includes non-stat buffs such as Armor March. While it provides less power than Wo Gùn+ (4 Attack when buffed compared to 10 extra damage on Specials), it also provides 4 Defense. In addition, it frees up the B slot to be used on a different skill such as Slick Fighter or Crafty Fighter, which both guarantee a follow-up on enemy phase as long as Flame Emperor is above 25% health while giving another helpful effect; penalty neutralization for Slick Fighter and slowing enemy Special activation for Crafty Fighter. Vengeful Fighter also provides guaranteed enemy-phase follow-ups, but the health threshold requirement for activation is stricter at 50% instead of 25%, and the Special acceleration on Flame Emperor’s attacks is generally not useful, since under most circumstances Noontime will activate on every counterattack. 
• Resistance is the ideal choice of boon, as Flame Emperor’s Resistance is much lower than Defense. Attack is also useful. Speed is the best choice of bane, since Flame Emperor’s Speed is already low and generally not useful. This build also functions perfectly well at neutral boon and bane if the player does not wish to spend Trait Fruits. 
• Distant Counter is necessary for Flame Emperor to counterattack ranged units. 
• Special Fighter provides Special acceleration while also slowing the Special activation of Flame Emperor’s foe. It is best used in combination with Quick Riposte seal in order to guarantee a follow-up on enemy phase. 
• The choice of C slot is flexible. Pulse Smoke allows Flame Emperor to inflict Special cooldown +1 on units within two spaces of the enemy after combat, which can be very helpful against teams with pre-charged Specials. A/R Far Save is also quite useful and allows Flame Emperor to guard allies within two spaces against ranged units that attack them. Many other choices of C slot can work; something like Armored Stride could be used for better mobility, or Atk Smoke to provide an Attack debuff to enemies after combat. 
• The choice of seal depends on the choice of Weapon and B slot. Quick Riposte is best used with Special Fighter. Mystic Boost can be used with a B slot that guarantees an enemy-phase follow-up like Slick Fighter, as it heals 6 HP after combat and disables the Wrathful effect of staves. Since Flame Emperor cannot counterattack healers using Dazzling Staff or similar effects, this can be useful to limit the amount of damage they can do. Atk/Res Bond pairs well with A/R Far Save, providing a boost to Attack and Resistance providing that Flame Emperor is adjacent to an ally, which includes an ally they are currently protecting with Far Save. Atk/Def Solo can be used for a slightly larger boost to Attack and Defense if Flame Emperor will generally not be adjacent to allies when in combat. 

Weapon: Slaying Axe+ (+Def) / Huge Fan+ (+Def) / Wo Gùn+ (+Def)

Assist: Rally Spd/Def+ / flexible

Special: Blue Flame / Ruptured Sky / Aether

IVs: +Atk / -Spd

Passive A: Distant Counter / Atk/Def Unity

Passive B: Special Fighter / Slick Fighter / Bold Fighter

Passive C: A/R Far Save / Joint Drive Atk / Any 300 SP C slot

Sacred Seal: Atk/Def Bond / Armor March / Quick Riposte 

• Flame Emperor is one of the highest base stat total 3-4 star units available in FEH, and can be used to great effectiveness on an arena team, taking advantage of high Attack and bulk and scoring quite well at +10. This build can also function well in other contexts where arena scoring is not a concern. In those cases, any of the skills used for their SP costs can be swapped out for others. 
• Using a Special like Blue Flame or Ruptured Sky (chosen for their SP cost for scoring), Flame Emperor can get attacked once by a foe and retaliate with a powerful counter, OHKOing a significant portion of common units. Blue Flame is generally stronger, dealing 25 extra damage provided Flame Emperor is adjacent to an ally, while Ruptured Sky’s lower cooldown enables more freedom with other skill choices. Aether can be used as a budget option, but doing so forgoes the ability to activate the Special on the first counterattack, which is the number one asset of this build. If used in modes where SP cost is not a concern, Bonfire can be used instead of Blue Flame, and Glimmer instead of Ruptured Sky. 
• The choice of Weapon and B slot depends on the Special used. Slaying Axe+ and Special Fighter are necessary to accelerate the cooldown of Blue Flame. If Ruptured Sky is used, the choice of Weapon is more flexible. Huge Fan+ provides Special acceleration on enemy attacks and can be used with essentially any B slot so long as Flame Emperor is receiving a bonus (a stat bonus or other non-stat effects such as Armor March). If Special Fighter is used with Ruptured Sky, essentially any axe can be used; Wo Gùn+ provides 10 extra damage on Special activation, improving all matchups, while Slaying Hammer+ allows Flame Emperor to better deal with armors. +Def is generally the most useful stat refine for all Weapons, since most common arena threats are physical, but +Atk may also be used for a slight power boost. 
• A 400 SP Assist such as Rally Spd/Def+ is necessary to maximize score. The choice of particular Assist is not important and essentially any option is fine. If used in a mode where SP cost is not a concern, Swap offers extra mobility and help in changing positions in crowded spaces, but the best Assist will depend on what the team needs. 
• Attack is the optimal boon for this build, since the point is to one-shot as many enemies as possible on the first counterattack, and Speed is the optimal bane since Flame Emperor’s Speed is already rather low and generally is not useful. However, this build functions almost the same at neutral boon/bane if the player does not want to spend Trait Fruits; Flame Emperor does not need a particular boon or bane to hit a certain base stat total in the way that some units do. 
• Distant Counter is highly useful to allow Flame Emperor to counterattack against ranged units. If this is unnecessary or unavailable, another 300 SP A slot can be used. Skills that boost Attack and bulk like Atk/Def Unity are ideal. However, giving up the ability to counter at range is generally not worth it. 
• The choice of C slot is flexible, with a 300 SP C slot being required for Flame Emperor to hit maximum scoring potential for arena. A/R Far Save can protect teammates from annoying ranged units while allowing Flame Emperor to potentially oneshot them with a Blue Flame or Ruptured Sky. Joint Drive Atk provides a mutual boost of 4 Attack to Flame Emperor and any allies within 2 spaces, so long as there is at least one ally within 2 spaces. Many other choices of C slot can also work depending on what is available.  
• The choice of seal depends heavily on the team. If Flame Emperor is used on a team with another armor unit, using Armor March on one of the units is highly useful for mobility. If this is not necessary, or no other armors are being used on the team, a seal that boosts Attack and Defense on enemy phase is ideal, such Atk/Def Bond. If used in arena, a seal that costs 240 SP is necessary to hit max scoring potential, which both of the aforementioned seals do. Quick Riposte can be used with Special Fighter in order to guarantee a follow-up attack; however, this is only useful if Flame Emperor does not KO the enemy with the first counterattack and survives the enemy’s potential follow-up. Other seals may also be used depending on the particular needs of the team. 

Weapon: Slaying Axe+ (+Res)

Assist: Reposition / flexible

Special: Galeforce

IVs: +Atk or +Res / -Spd

Passive A: Atk/Res Unity / Distant Def

Passive B: Bold Fighter

Passive C: Armor March / flexible

Sacred Seal: Distant Def / Armor March / flexible

• Flame Emperor can utilize a set relying on Bold Fighter’s Special acceleration to activate Galeforce. This build is best used in combination with another armored unit using galeforce, so that both units can gain the increased mobility from Armor March and KO several units, leaving one or two weak units standing, then use their high bulk to survive any attacks those units make on enemy phase. 
• Slaying Axe+ is necessary to reduce the cooldown of Galeforce to 4, allowing it to activate after two attacks made with Bold Fighter, providing the Special activation is not slowed in any way. +Res is generally the best refine for increasing Flame Emperor’s bulk. 
• Reposition is a good choice of Assist that is useful in many contexts, but others may be used, this slot is flexible. 
• Attack and Resistance are both solid choices for boon that increase Flame Emperor’s damage dealt and survivability, respectively. Speed is the best choice of bane, since Flame Emperor’s Speed is already poor and usually unnecessary for follow-up attacks when using Bold Fighter. This build also functions almost as well with neutral boon and bane if the player does not wish to spend Trait Fruits. 
• The choice of A slot is flexible; the listed options provide good bulk on enemy phase, while also providing some extra power in the case of Atk/Res Unity. 
• Armor March is very useful to have on either Flame Emperor or the other galeforce armor, in either the C or S slot, as it is much easier to initiate on enemy units with the extra tile of movement. Other useful C or S slots are any that increase Flame Emperor or other armors’ bulk on enemy phase, such as Distant Def, Ward Armor, Mystic Boost, or many other possible options. If Flame Emperor is used without a partner, Armored Stride provides more self-sufficient mobility.