Ephraim

• Preferred IVs: +ATK or +DEF / -SPD or -RES
• Weapon: Siegmund (+Eff)
• Assist: Reposition / Rally Defense
• Special: Aether / Glimmer / Bonfire
• A Slot: Death Blow / Sturdy Blow / Heavy Blade
• B Slot: Vantage / Wrath / Renewal
• C Slot: Odd Atk Wave / Hone Spd
• Sacred Seal: Heavy Blade / Fortify Res / Attack + 3

With this set, Ephraim gives up some of his support utility to become an extremely potent offensive unit. With his weapon's ability to strike twice with high HP, his priority then falls to ensuring that his HP remains above the threshold as much as he can. This is done one of two ways:

• Heavy Blade (as an Attack boon Ephraim with Death Blow reaches 58 Attack), Aether, and Vantage: Ephraim's guaranteed double and significant chance of Heavy Blade proc ensures that after his first combat, he will have Aether primed and ready to fire. If he is within Vantage range, he will attack the next enemy who initiates on him with Aether in the following Enemy Phase. Ideally, this will kill his opponent and allow Ephraim to heal himself to where he will be in range for his weapon to proc the double attack again.
• Sturdy Blow + Renewal is less risky, with the bonus of being able to proc a guaranteed Glimmer during your first turn. However, with this, Ephraim relies on Sturdy Blow's Defense bonus to prevent him from taking too much damage on the retaliation and then falls back to Renewal to heal up what he might have lost. This Ephraim will have difficulty healing off more damage within a respectable amount of time. Also, Sturdy Blow's Defense bonus is useless when attacking dragons or mages with Close Counter.

Wrath is the ideal A slot for Ephraim if you intend on running him as a strictly Player Phase unit, as it will help to mitigate the cooldown of Aether if he's below the threshold of doubling. This means that even if he doesn't have Aether primed at the end of his first combat, Wrath will allow him to prime it before his next combat, as well as offer him additional damage that he can use to further heal himself back into the range of Siegmund's pursuit effect.  However, if Ephraim is at risk of being attacked after his first engagement, then Vantage would be a better pick, as it will allow him to attempt to finish off his opponent before he takes further damage in Enemy Phase.

If he's lacking a buffer on his team and you want Ephraim to be a full offensive powerhouse, rather than a hybrid damage/support, then Odd Atk Wave is his ideal choice in C slot. This skill will offer him 64 Attack on initiation, giving him a more reliable shot at activating Heavy Blade for more damaging Specials. If using him as a buffer, it still benefits his team for him to run Hone Spd in his C slot more than most other C slot buffs to ensure that he's still capable of buffing a potential ally, and since Speed is Ephraim's dump stat, he's more suited to giving away that particular buff than any other.

• Preferred IVs: +ATK or +DEF / -SPD
• Weapon: Flame Siegmund 
• Special: Aether / Dragon Fang / Ignis
• Assist: Smite / Shove / Reposition
• A Slot: Death Blow / Steady Breath / Fury
• B Slot: Wrath / Desperation / Chill Def
• C Slot: Odd Atk Wave / Threaten Def
• Sacred Seal: Heavy Blade / Close Defense

Legendary Ephraim's introduction to the game allowed for his initial infantry form to inherit the Flame Siegmund, a powerful legendary weapon which offers Ephraim the ability to secure a followup attack, as long as there are more opponents around him than there are allies. Unlike Siegmund's initial enhancement, Flame Siegmund works in both phases and has no HP requirement, which offers much more flexibility in his build options.

This does come with the drawback of eliminating Ephraim's support capability, as his Siegmund's natural Attack buff to allies is applied only to himself when he wields Flame Siegmund.  In addition, it makes him far more reliant on positioning which may be more difficult in tightly-packed maps, particularly due to Ephraim's 2 tile movement as opposed to Legendary Ephraim's 3 tile movement.  Due to this, Flame Siegmund can be seen more as a sidegrade than a direct upgrade to a refined Siegmund.

Despite the drawbacks, the ability to double in Enemy Phase as well as Player Phase negates the necessity for Quick Riposte, which opens Ephraim's B slot to run lethal skills like Wrath, Chill Def, or Desperation. Guard is another option for a more defensive Ephraim, however its stringent HP requirement does not play well with Ephraim's lone warrior playstyle.

Death Blow would be Ephraim's preferred A slot if the intent is to run him predominately in Player Phase, however if you'd rather use him as an Enemy Phase tank, then Steady Breath would be optimal, and for a flexible Mixed Phase option, Fury is the best skill which grants him Attack and Defense at all times.

Heavy Blade is a no-brainer for a Player Phase Ephraim (though note that it will not stack with Steady Breath on Enemy Phase), and it will likely proc due to his 63 Attack (69 if self-buffed with Odd Attack wave). This allows for longer cooldown specials such as Aether to heal off damage, or Dragon Fang, which would hit for an additional 45 damage with his Death Blow/Wrath/Odd Atk Wave set.

Ignis is another option of Special, which would be run primarily on an Enemy Phase Ephraim who would rather take Close Defense Seal due to Heavy Blade's lack of Synergy with Steady Breath. A +Def/Steady Breath/Wrath/Close Defense build allows his Ignis procs to hit for an additional 46 damage.

Smite is chosen as his Support skill to help him fulfill the requirements of his Flame Siegmund, by forcing his allies away from him in order to keep him outnumbered by his opponents. Smite may be best served on an Enemy Phase oriented Ephraim, as he would spend his Player Phase pushing his allies away from him.

• Preferred IVs: +DEF or +RES or +ATK / -SPD
• Weapon: Siegmund (+Def) / Siegmund (+Res)
• Assist: Reposition / Rally Defense
• Special: Aether / Ignis / Glimmer
• A slot: Steady Breath / Distant Counter / Close Defense
• B slot: Quick Riposte / Bowbreaker / B Tomebreaker
• C Slot: Odd Atk Wave / Hone Spd
• Sacred Seal: Close Defense / Distant Defense / Heavy Blade

Although his prowess during Player Phase is remarkable, Ephraim functions very well as an Enemy Phase tank, particularly when stacking his defenses and utilizing skills such as Steady Breath and Quick Riposte.  With a boon, his Defense hits 35, and further increasing with Defense forge/Steady Breath/Close Defense gives him an unbuffed Defense of 49, which is more than enough to fend off melee attacks from powerful reds and blues alike. When combined Aether, Ephraim can use his Special in the first engagement if doubled (as he should be, with a bane in Speed) and heal off the damage he's taken in that particular engagement. This set leaves him very vulnerable to magic and dragons, an issue which is solved in his next iteration of this build.

With a Resistance boon and forge on Siegmund, Ephraim reaches a Resistance stat of 27. With a Distant Def seal added in, his Resistance stat when attacked by a mage grows to a decent 33 with no outside support. This allows him to be a remarkably decent ranged counter, capable of striking back against tomes and bows alike.  With this set, he can eliminate magical threats such as Delthea, Linde, and Christmas Tharja, as well as bow units and daggers, such as Bridal Cordelia or Klein.

Ephraim can also run Glimmer in an attempt to KO opponents with Brave weapons, as he will retaliate with a charged Glimmer shot on his first attack. With a Resistance-focused set, Ephraim can barely survive an attack from an unmerged Attack boon Death Blow Reinhardt, but will require buffs to his Resistance to survive him if the Reinhardt is significantly merged or buffed.

• Preferred IVs: +ATK or +DEF or +HP / -SPD
• Weapon: Siegmund (+Eff) / Siegmund (+Def)
• Special: Glimmer / Aether / Bonfire
• Assist: Rally Defense
• A Slot: Triangle Adept / Steady Breath / Death Blow
• B Slot: Renewal / Quick Riposte / Wings of Mercy
• C Slot: Hone Spd
• Sacred Seal: Fortify Res

With this set, Ephraim's primary focus is buffing his teammates and acting as an anti-red unit. He does this by sacrificing his Assist, C slot, and seal slot in order to give maximum buff potential, for an impressive +4/+4/+4/+4 buff.

However, that does not necessarily mean that his combat ability is gone, as Ephraim is still able to double on initiation with his forge. He can also continue acting as a good blue defensive tank, walling and taking down enemy walls for your team.  His A slot goes to Triangle Adept, which will make him your team's guaranteed anti-red unit and give him optimal matchups against even red mages who might otherwise pose a threat to him. Alternatively, you can give him some semblance of his above build with a combination of Death Blow and Renewal, which utilizes his forge's effective ability while retaining his support utility.

Steady Breath and Quick Riposte are also very viable options, which would work best with a Defensive refine on his lance. This turns Ephraim into a defensive tank, capable of unleashing Aether Special procs and healing off any damage he might receive.  While giving him his special Pursuit forge on his lance allows him to more safely take down the likes of Ayra, Soleil, Mia, and Karla, his general sustain and capabilities as a generalist are more favorable with a more Enemy Phase-focused build. 

He works best with green bladetome mages, such as Nino or Rhajat, due to his ability to provide buffs while also easily dismantling any red unit who threatens them, though he can be a benefit with any sort of bladetome on his team.