Brave Lucina

My Brave Lucina with favourable boon/bane combination for a bulkier which doesn't rely on a large HP pool but rather sustain through self healing and strong Def, Spd, and Res stats.

Geirskogul, Drive Spd, and Spur Spd seal makes her an outstanding support unit, while her well rounded stats and strong sustain makes her a strong unit in her own right.

Ardent Sacrifice works well with the rest of her build, giving her additional utility as a healer whenever she has to stay clear of enemy units.

+ speed Brucina. No worries about getting doubled with this boon. She’s definitely a fantastic support weapon for melee, bow and dagger weapons. Poison strike helps soften up enemies nicely so another teammate can finish them off. Quicken pulse helps her get Aether to trigger sooner if need be.

B!Lucina doesn't run a typical Fury Renewal Reciprocal Aid build like her regular form does because of a lack of a Falchion passive healing, but uses it to keep herself alive and support her teammates.

A defense boon gives her the greatest increase in stats for arena, and with Fury her speed will be high enough to avoid being doubled. With Geirskogul, Drive Spd, and Rally Atk/Spd, she becomes debatably the best buffer in the entire game for physical units (in competition with Delthea). Those three items grant any physical teammate melee or ranged, up to +6 atk and +9 spd by herself alone; that's incredible for infantry support.

Bonfire will be her special of choice, because she will more than likely engage only when she has the complete advantage so as to stay healthy, and thus will not be getting as many Moonbows off as one might think.

*Stats shown with Weapon and Defence +1 Sacred Seal*

Weapon: Geirskogul
Assist: Reposition / Rally / Pivot
Special: Ignis / Bonfire / Aether
A-Slot: Steady Breath
B-Slot: Quick-Reposte / Vantage / Wrath / Renewal
C-Slot: Drive Speed / Drive Attack
Sacred Seal: Defence +1 / Speed +1 / Distant Defence 1

Enemy phase Lancina. +Def/-Res or +Spd/-Res

This build utilises Steady Breath and Quick Reposte along with her speed to ensure she kills every non ranged unit that attacks her.

The idea of this build is for Lucina to first take a hit from the enemy reducing Ignis to 2 CD, retaliating back and charging Ignis in the process, then due to her speed and QR she will now perform another uncontested follow-up attack proc-ing Ignis and dealing 28 - 30 (31 with Seal) extra true damage, killing anything that's not a high defence green.

Bonfire is also an option with QP allowing Lucina to proc it on her first retaliation, however due to the affects of Steady Breath and Bonfire's 3 turn CD, it can be difficult to utilise after the first hit.

Another option that can also be ran is her default Aether to improve both sustainability and her Arena weighting. With Steady Breath and QR she can bait and kill a lower defence unit with her 50 base attack and have a fully charged up Aether ready to go for a fresh new unit on the next turn.

And lastly, her default Sol can also be used in the same way as Ignis allowing her to heal up her HP in order to stay in QR range and improve her sustainability.
However, due to the fact that Lucina already hit the enemy and reduced their health, the healing might not be sufficient when Sol procs. This means Aether is actually a far better option, but Sol is still feasable.

For her B-Skill, QR is not necessarily if you think Lucina is fast enough, but since the build requires a double attack to work, QR is recommended.
However, if one does not wish to run QR, Vantage is also a fantastic option.

With Vantage and the assumption that Lucina will still double, the first round of combat will still proceed as planned. If she did not double, she will have a fully charged Ignis on player phase. Either way, she'll most likely be in Vantage range now.

If she did double on the first round of combat, Vantage now allows her to attack first on the next round of combat potentially killing a weakened enemy and reducing Ignis to 2 CD.
If the enemy did not die however and continues to hit Lucina, this will charge Ignis to full and either allows Lucina to kill them on her follow-up or have a fully charged Ignis for player phase if she's not fast enough.

If she did not double on the first round of combat, she will most likely kill someone with the Vantage!Ignis combo and reset. If she for some reason did not kill them and gets hit, they'll reduce Ignis to 2 CD again, and if she doubles she'll definitely kill the attacker and have a fully charged Ignis either way.

Another option for her now is Wrath, which can synergize amazingly as both an offensive option and a defensive safety net.
With Wrath, Lucina will be able to safely enter Wrath range due to her fantastic defensive bulk, allowing her to pump out some very powerful Ignis/Bonfire procs, capable of ORKOing anything that dares to touch her.
However, with Sol/Noontime/Aether, Wrath will act as a safety net, allowing a weakened Lucina to passively charge her healing Special and allow her to proc her special with an extra 10 damage, healing for a potential 5 extra HP.

The final option for her B-Slot is Renewal, this relies on +Spd variants of Lucina to reach 44 speed with Speed Seal and Hone Speed in order to double the majority of units she needs to double whilst using her the sustainability with Renewal to run the Ignis set into multiple enemies.

As for her Assist Skill, Reposition/Swap are the most useful for her role, however a Rally or Pivot can be ran to fully embrace her support potential.
With Rally she can buff even more skills at the cost of her team mates mobility, and with Pivot she can literally have coverage of the entire map with her buffs due to the mobility it gives.

Fairly standard/budget setup. Lancebreaker is taken as a relatively neutral B-slot skill, which can give a bit of an edge in lance-vs-lance fights. Her default A- and C-slots give her raw stats and support presence, while Swap is added primarily as a way for her to shift less bulky allies back to the middle of the team while also keeping herself in the front lines to continue providing buffs.

As a bit of a gimmick, I also have Obstruct as a B-slot option for her to run, offering a fun little synergy with Swap to completely wall off an ally providing the other conditions are met.