Sophia

This build is specifically made to capitalize on the Brash Assault seal, so if you don't have, this build COULD work with the B-skill, but it works far better with the seal. Any boon will work, barring Speed, and -Speed is really the only bane you want, although -HP and Ardent Sacrifice will speed up the process of getting to that 50% (Reciprocal Aid is used for allowing her to heal low HP allies to take that low HP). Even neutral will work, just don't hinder her fire power. For the A-skill, while anything that either ups her defenses or offense will work, Defiant Atk 3 is recommended as it makes sure she one-rounds, which is needed as if she takes a single hit while under 50%, she's probably done for. Desperation 2 is the recommended B-skill as it allows her to get both attacks in without risk of getting attacked, basically giving her a pseudo-red Dire Thunder, and Desperation 3 is just overkill. The only thing she'll really be doubling is Arden and even then, he can't counter unless they're running Distant Counter for whatever reason, so Desperation 2 is cheaper and all that's really needed. C-Skill can be anything you want, and while buff skills are recommended, Res Ploy or Threaten Res can be used to potentially up her damage output. Brash Assault 3 seal MUST be used for everything to work (Although it still functions fine with 2). Weapon is Fenrir+ for budget reasons, since this is a semi-budget build, and all you really need is some fire power, although a def forged Wolf tome works too. Just use an HP lowering skill for Support skill. Special is Dragon Fang for budget, although Ignis can also work, or Glacies, depending on which defensive stat you want to increase. All in all, it's a frail build, that does require her to survive hits, but it can be a counter to a lot of common arena threats, most notably, Hector and Brave Lyn (Especially the latter, since she can survive a round with +Def boon and Def forge, and get in Brash Assault/Defiant/Desperation range).

SHE SO GOOD!!

If you want a Brave Lyn/Archer counter that charges up a nuke after being initiated on look no further! Also, she WILL 1vs4 some games in Arena Assault.

However... This build sucks for everything except using that nasty Ignis nuke:
+ATK really is that much better for her game; She doesn't make any significant use out of any of the seals.

Sophia's ideal Arena build goes something like what I have, with these changes:
- + ATK IV's.
- replace Ignis with Moonbow.
- apply Quickened Pulse.
- replace QP 3 with Swordbreaker.

I wanted a quality of life unit to use in Arena Assault, and I'm super satisfied with the results :D

Two words: MAXIMUM POWER!!! I chose Death Blow over LaD for 2 reasons. 1. Sophia's speed isn't very good. 2. Death Blow gives her more attack while not compromising her defenses. B Tomebreaker allows her to hopefully use her high attack to nuke blue mages faster than her (Reinhardt, Mae, Linde). Threaten Res is used to poke holes in enemies in tanker enemies and to help secure kills. Fenrir+ is used for maximum damage, as 13 might is quite high. I would use Raourblade+, but being an infantry unit, she doesn't too many chances for buffs. Pivot is used to quickly dip out if things get hectic. Dragon Gaze is used to deal the highest damage possible with her high attack.

I like to call this set the Red Robin for reasons that should really be apparent.

The focus of this build is to have Sophia check Red Tome units (all of whom double her, as she has the second lowest speed in the game) and wall out Greens and Colorless (who don't run Cancel affinity). If they do run CA you can instead have her run Earth Boost, because most archers and daggers have 40 or less HP even when merged to +10, so an HP seal will allow her to tank CA units and kill on counter with QR.

As this Sophia doesn't run Close Counter she should leave Sword units to another teammate, and is completely fine with taking a hit from melee greens then proceeding to eradicate them next turn.

Sophia prefers an Atk boon, and since her speed is simply abysmal, we're gonna go ahead and feed that to the sharks; so her bane is speed. Taking advantage of the fact that she has bad speed, she has Draconic Aura as a 3 turn special, well, because she's a dragon and also cause she'll reach her special faster thanks to being doubled; nuff said. If she has a Res boon, she can opt to run Iceberg instead and an Atk Ploy C skill.

Reciprocal Aid and Breath of Life allow her to act as a passive healer. She can also utilize RA to heal herself when needed.

With the Distant counter 1 seal and a breaker skill of choice, Sophia is a strong tank without the use of tri-adept. You can always sub tri-adept for most cases, but it leaves her weak to cancel affinity.

An effective 47 defense to archers means brave bow archers barely dent her.

A breaker skill of choice allows for additional coverage for swords, axes, or red tomes. And helps her tank those types better.

The addition of merges and summoner/ally support only increases her viability as a mage-tank, and cements her role as a 0x2 character.