Delthea

Weapon: Dark Aura (+Eff) 

Assist: Positional Assist / Flexible

Special: Moonbow / Luna 

Passive A: Fury / Fort. Def/Res 

Passive B: Sabotage Skills / Chill Skills / Flexible

Passive C: Joint Drive Atk / Joint Drive Spd / Drive Skills / Tactic Skills / Flexible 

Sacred Seal: Drive Atk / Drive Skills / Tactic Skills / Phantom Res

• Delthea’s Dark Aura enables the young girl to act as a respectable support unit to other melee allies, providing an ample boost to their firepower, while still retaining some of her combat prowess. A +ATK or +SPD IV work well to supplement Delthea’s offensive potential, though +RES may also be worthwhile if a more supportive lean is preferred. 
• Fury provides the greatest overall boost to Delthea’s performance on both fronts, augmenting her offenses while also aiding her ability to utilize Resistance-scaling skills like Sabotages; it also helps offset her poor Defense. If focusing solely on her supportive utility (and thus want to maximize her chances of landing Sabotages), Fort. Def/Res is a solid—but high-investment—alternative. 
• Her B slot is ideally filled by either a Sabotage skill or a Chill to stack debuffs on top of the buffs she provides. The choice between which one depends on personal preferences as well as what skills and IVs are available, since Delthea’s Resistance requires investment to fully leverage Sabotage skills—and Sabotages themselves are somewhat rare.
• For Delthea's C slot and Sacred Seal, any skill that further assists her team—such as Drives, Tactics, and Chills—should be equipped. Joint Drive skills pair quite well with Dark Aura’s effect as she needs to be near her allies regardless, and the Phantom Res seal may be worthwhile with Sabotages to help ensure it lands. 

Weapon: Blárblade+ 

Assist: Positional Assist / Flexible 

Special: Miracle / Glimmer / Moonbow 

Passive A: Close Foil / Close Counter

Passive B: Vantage

Passive C: Pulse Smoke / Res Smoke / Flexible

Sacred Seal: Heavy Blade / Atk/Def Solo / Fierce Stance / Brazen Atk/Spd

• Delthea’s strong base Attack and access to a Blade tome allows her to make pretty good use of a standard Vantage setup, focusing on her ability to consistently OHKO opponents during the Enemy Phase. An Attack Asset is preferred to frontload as much damage as possible. 

• The primary strategy here is to combine Vantage with an ability that enables counterattacks regardless of range to cleanly sweep through incoming enemy forces, provided she loses enough HP prior. For the purpose of Aether Raids Offense, Close Foil works as a better alternative to Close Counter given how uncommon dragons are on Defense teams; however, Close Counter may still be used to stay safe.

• Miracle works excellently to provide a bit of safety to Delthea’s playstyle, since taking damage may not always be avoidable—even with Vantage. It does require the use of the Heavy Blade Sacred Seal to charge up quickly, though. If a damage-dealing Special is preferred, low cooldown options like Glimmer and Moonbow are recommended. 

• Pulse Smoke is an excellent C slot in the context of Aether Raids Offense to shut down compositions centered on instant Special activations; otherwise, Res Smoke provides more general coverage. For her Sacred Seal, if Heavy Blade is not being used, an Attack-increasing seal may be taken as a substitute.

Weapon: Blárblade+ / Flora Guide+ (+SPD)

Assist: Positional Assist / Flexible 

Special: Glimmer / Moonbow / Draconic Aura

Passive A: Atk/Spd Solo / Swift Sparrow / Atk/Spd Push / Sturdy Impact / Fury

Passive B: Desperation 

Passive C: Rouse Atk/Spd / Wave Skills / Res Smoke / Drive Atk / Flexible

Sacred Seal: Swift Sparrow / Heavy Blade / Flashing Blade / Death Blow / Atk/Def Solo

• This has Delthea adopt a more traditional offensive playstyle and centers around her combat performance during the Player Phase. Increasing either of Delthea’s offensive stats will be appreciated to supplement her damage potential either through stronger individual hits or more consistency in doubling opponents. 

• Although a Blade tome is a common weapon pick for such a playstyle, it does come at the cost of making Delthea dependent on receiving visible buffs to function—and conversely, renders her incredibly weak to sources of Panic. For more self-sufficiency, a Speed-refined Flora Guide works well as an alternative.

• Delthea’s A slot can be occupied by any standard offensive option—such as Atk/Spd Solo, Swift Sparrow, Atk/Spd Push, and Fury—and the same applies to her Sacred Seal, if Heavy Blade or Flashing Blade isn't being used there. For additional safety, Sturdy Impact may make for a worthwhile consideration, but it is rather costly. Desperation is a necessity to circumvent Delthea’s abysmal physical bulk.
• Although she doesn't have a preference for any particular C slot, Delthea does have some standouts available; this includes self-buffing skills such as Rouse Atk/Spd and Wave skills to make her less reliant on team support, and Res Smoke if refresher support is available. Otherwise, she can equip anything that best suits her team, like her base Drive Atk.