Legendary Robin (F)

5*+10

Mixed phase monster. More than capable of taking out an enemy in player phase and taking out any enemy unfortuante enough to attack into her afterwards.

A SKILL
F!Grima's defences are already rather solid, and her HP provides a good amount of bulk, even with L&D applied; her bulk remains around 70 for both physical and magical damage.
While Dragon Skin is a good skill, it isn't enough to pull her together, and isn't substantial enough to build a kit around. As a colourless unit F!Grima can have trouble dealing and tanking damage. All other units can use colour advantage to give themselves a +20% to their stats; F!Grima doesn't have this luxury. Also, since she is a flying unit she cannot use any of the most potent enemy phase skills, such as Wary Fighter or Steady Breath.

B SKILL
Vantage allows F!Grima to tank effectively. It effectively makes her immune to mages, as most that populate arena have minmaxed stats; high RES, low DEF. It also allows her to deal good damage, or potentially kill any melee unit that comes into combat with her, as most have low REs and high DEF. Setting up opportunites for Vantage to take out enemies is pivotal to the build, and planning should be done accordingly.

C SKILL
Eh, it doesn't really matter. Res Smoke allows her to do more damage in both player and enemy phase, so that's cool. But really, anything can go here. Tactic skills, Flyer skills, whatever.

SEAL:
Heavy Blade allows her to make further use of that sky high attack. Assuming she can pull of a one hit kill in her first turn she can destroy the next unit to attack her (with a few exceptions). You can't go wrong with Heavy Blade.

Weaknesses:
The most obvious is archers. Sacrificing Dragon Skin for L&D removes her immunity to archers. This isn't really a deal breaker though. Create a bow countering unit to support her.
Tiny hand horse meme man can also one shot her with his most popular build. This is a bit more of a deal breaker, but isn't too bad, most people have a Rein counter or two.
Raven tomes with Triangle Adept. These will destroy her, letting her fall victim to all the Cecilias that were built to counter Rein & B!Lyn (who both counter F!Grima hint-hint). Again, you'll need another unit to take care of Raven tomes.

Being the new fastest dragon, she is naturally the best user of the Dark breath/Sweep combo. Dark Breath +speed is to push her speed over 40 and dark breaths devastating debuff. Moonbow is here because she doesn't have access to cooldown reduction outside of heavy blade. Distant counter is here because dark breath works on both phases. Alternatively you can lose out on the ability to counter attack mages for dragonskin as a budget option, with dark breath creating a 11 point total difference in their attack to your def/res. For the B slot either Sweep skill can work. For the C slot I put guidance for mixed teams, and dragon teams that contain her male counterpart. Alternatively any dragon or flier buff can work for her given team. For the Sacred Seal I gave her phantom speed 3 to almost completely guarantee her sweep activating, this can be replaced with speed +3 for the added benefit of preventing doubles on non debuffed units, guidance seal for air dropping powerful units onto debuffed ones or... heavy blade (only recommended with heavy buffs in attack and speed with aether)

Preferred IV spread: -Atk / +Spd

Assuming her team contains one hone fliers, fortify fliers, and a goad, she's looking at 55 points of neutral magic Atk with 48 Spd to double and prevent follow-ups from just about any unit. On enemy phase she's able to shrug off attacks from most units with dragonskin and fortify granting her 40 Def and 35 Res.

Expiration is essential to her set up as a mixed tank and it's 16 Mt effectively mitigates her 29 Atk. However, if you're willing to sacrifice 4 Atk, you can invest in Lightning Breath+ (+Res) for an additional 5 hp and 4 Res to secure better survivability.

Sol's cooldown of 3 and her ability to counter anybody leaves Robin at full hp fairly consistently. And being the hp spout that she is, she's able to take advantage of Reciprocal Aid to keep her frail flyer partners in the game longer. Aether is an option, although her attack and speed usually makes the "Luna" effect superfluous while the faster cooldown keeps her more regularly healed. Not to mention that inheriting an Aether is a much bigger investment.

Dragonskin's great! Bracing Stance and Iote's Shield all in one. yeah, why not?

On a mixed tank Quick Riposte can go a long way, but with this build's top Atk/Spd of 55/48 safely frees up the B slot for more utility. Vantage is for survivability and it works like a charm. if a battle ever leaves her under 75 hp she'll get the drop on the next unit that attacks her, Sol ready -or ready enough- to get her hp back up and avoid fatalities.

Smoke synergizes exceedingly well with Robin's innate distant counter, crippling anyone within 2 spaces of any unit that may attack her. Default Res Smoke with the Atk Smoke seal gives enemies within a large area of a effect a massive offensive and defensive penalty for your entire team to benefit.

Preferred IV spread: +Atk, +Spd or +Res / -Hp

Female Grima can be a powerful asset to a team of fliers or dragons, with her coordination being great with certain units from both groups. This set emphasizes FGrima's potential for a neutral and balanced defensive spread that works against enemies of any range.

There are multiple choices for the IV spread, with the boon preferably being in speed to truly bring that naturally high base to a respectable level, followed by attack to generally increase the damage output, and resistance to balance the defensive spread out on the high-end, while also running that +4 from it being a superboon. With everything being more or less important on her, dropping Hp is a safe decision.

Her default skillset already brings a lot of potential that can be optimally utilized. We can, however, do some tweaks here and there.

Expiration is preferred over a refined Lightning Breath+ due to there being a major enough difference in Mt between the two and the former also not prolonging the special charge. Any other Breath can be considered for specific purposes, but due to her wanting to mainly be a mixed EP tank through this set, an inbuilt DC is essential.

Aether or Ignis can be taken as the special, with the former being preferred to increase the survival rate. The default Bonfire isn't recommended, especially when investing in the speed factor through nature, as FGrima will not get doubled much, resulting in the EP combat ending with a fully charged special for any special with a cooldown of 3 or more. Those will activate in the second encounter, at which point anything can be taken, with Aether potentially serving the purpose the best.

Dragonskin is a very handy A slot skill to run, as it packs Iote's Shield and Bracing Stance in a single slot. The former allows for bow checking specialization in a fliers team, while the latter further compliments both def and res on an already-balanced defensive spread.

Quick Riposte is used to ensure doubling during the EP. In essence, the boon in speed works mainly as a defensive approach to prevent being doubled. While 38 speed is respectable, it is many times enough to prevent being doubled, but not to ensure doubles. Here is where QR performs its part, to force getting hit once and retaliating twice.

Default Res Smoke also compliments well with FGrima's stat focus, as she does not really hold an overly high amount of attack. Due to that being the case, battles can get prolonged. Should they enter the second encounter, not only would the high-end specials be charged from the previous points, but Res Smoke would also apply, granting even greater damage output and assuring a KO.

Seal generally wants to further emphasize her defenses. Should her position be to tank bows and mages, Distant Defense works extremely well. Close Defense can be considered, should she want to counter range 1 units, but she has much more viable competitors in this field that on range 2, hence Distant Defense is preferred in most team compositions.