Eir

Preferred IV: +RES / -HP or -DEF

Weapon: Temari (+RES)

Assist: Smite / Flexible

Special: Moonbow / Iceberg / Luna

Passive A: Fort. Def/Res / Fury / Fortress Res

Passive B: Sabotage Skills / Disarm Trap / Link Skills / Chill Skills 

Passive C: Sparkling Boost+ / Flexible

Sacred Seal: Ground Orders / Phantom Res / Guidance / Aerobatics / Chill Skills / Drive Skills / Tactic Skills

• Eir was tailor-made for defensive strategies within Aether Raids Offense: by merit of merely existing on a given team during Light Season, she immediately grants an effective +10 Resistance to all allies and the most wounded teammate is automatically healed for a whopping 20 HP each turn. This build aims to just build on this innate supportive utility, firstly by replacing Lyfjaberg with Temari to add another layer to her support via debuffs. 
  • Although she can work perfectly fine with a neutral IV set, Eir benefits quite a bit from receiving +RES if available to improve the consistency of the mass debuffs she can apply via Temari and potentially Sabotage skills. 
• Fort. Def/Res is Eir’s ideal choice of A slot if aiming to invest fully into stacking her Resistance to further augment her ability to land her debuffs, with the decrease to her Attack being entirely negligible since she likely won’t be engaging with opponents to begin with. If unavailable, Fortress Res is an excellent alternative or if wanting to preserve her combat ability while still boosting Eir’s visible Resistance (though to a lesser degree), Fury can be considered as well. 
• For her B slot, Eir has several readily available options depending on player preference:
  • Since Temari already applies a notable debuff to her foes’ Attack and Speed stats, one invest further into Eir’s debuffing capabilities either with a Sabotage skill (which shares a similar activation requirement to Temari) or a Chill; the choice between taking a Defense debuff or Resistance debuff, though, will depend on what type of damage the main carries specialize in.
  • Disarm Trap is a highly specialized, but interesting choice to safely test out enemy traps in Aether Raids and improve her allies positioning flexibility upon disabling them. However, since most traps are within close proximity of the actual opponents, using this skill does require a bit of finesse to fully utilize and will usually mean the assistance of a refresher or an outside ally.
  • Link skills are useful to apply strong bonuses to various stats at once, allowing her to wield buffing and debuffing utility simultaneously; these skills also pair well with Smite to strengthen her intended ally while also allowing them to easily close in on the enemies. The preferred choice will once again depend on player preference, but having it provide at least a Resistance buff may be ideal given the context of AR Offense where magical damage is highly prominent. 
• Her exclusive Sparkling Boost+ should very rarely be replaced, as it can contribute majorly to her allies’ overall survivability; a passive 20 HP heal and +5 Resistance boost that can be applied regardless of where Eir is on the map is very hard to pass up on for tanking purposes. Still, for those deadset on replacing it, some alternatives include movement-based support C slots like Guidance or simply any available selection of Tactic or Drive.
• The Phantom Res Sacred Seal fits excellently with this build’s intended purpose, assisting Eir in landing Temari’s debuff and potentially that of Sabotage skills if equipped; this may be of especially high value if using a neutral Eir, since she’ll need all the help she can get in boosting her base Resistance of 31. Any choice of Drive, Chill, or Tactic skill or Ground Orders/Guidance for movement support may also be considered.

Weapon: Pumpkin-a-Box+ (+ATK/SPD) / Lyfjaberg

Assist: Reposition / Flexible

Special: Moonbow / Glimmer /Ruptured Sky

Passive A: Fury (3 or 4)

Passive B: Disarm Trap / Desperation / Escape Route

Passive C: Savage Blow / Spd Smoke / Atk Smoke

Sacred Seal: Fury

• Although this build once again assumes the context of Aether Raids Offense, it’s instead centered around Eir’s place in Galeforce-centric teams by becoming a beacon for other allies equipped with Wings of Mercy, with this strategy being more commonly known as “Eirforce.” The relevance of this strategy has admittedly faded quite a bit since the introduction of Ninja Lyn and Save skills, but it’s an option nonetheless that works decently enough with caution. A neutral IV set will once again work fine, though a boost to either one of her offensive stats is more than welcome. 
• The main gameplan here is relatively straightforward and centers around lowering Eir’s HP below 50% with as minimal engagements as possible (maximum of two) for her allies to use her as a beacon for quick access to the enemy team, and there’s a few ways this can be achieved. 
  • Replacing Lyfjaberg with Pumpkin-a-Box and equipping Fury 4 in her A skill and the Fury Sacred Seal offers the greatest amount of safety as this automatically inflicts an entire 20 chip damage — enough for the princess to immediately drop down below 50% HP in one round of combat. This minimizes the risk of having Eir potentially falter due to subsequent rounds of combat and frees up refresher actions to actually assist those engaging in the Galeforce chain. 
  • This combination works up until she reaches 41+ HP, which should cover most players even during her bonus weeks unless she’s slightly merged at which point she’ll need refresher support to drop into Wings of Mercy range — there’s just no other way around it. 
  • At this point, though, it does ease her inheritance requirements since she can actually keep her base Lyfjaberg (note: not refined) and equip the widely available Fury 3 with the Fury Sacred Seal; this inflicts 16 chip damage and ensures Eir can act as a beacon within two engagements up to an HP cap of 64. This strategy also works decently for those aiming to invest minimally and who don’t mind using a refresher action for Eir to achieve her goal.  
• Beyond the self-inflicted damage component of this set, there are other considerations to make. In particular, Disarm Trap is highly recommended to allow Eir to safely carry out her setup without worrying about trap placement disrupting this strategy — while it is possible to use her without Disarm Trap, doing so involves much higher risk. If unavailable, B slot skills that operate at low HP (e.g. Desperation, Escape Route, etc.) are possible alternatives. 
• Using Savage Blow as her designated C slot is effective for allies to more easily sweep through the enemy forces, allowing them to potentially KO foes in a single hit. Alternatively, Spd Smoke or Atk Smoke can be equipped if her paired teammates are dependent on skills like Flashing Blade or Heavy Blade to accelerate their Special charge.

Weapon: Lyfjaberg (+EFF)

Assist: Reposition / Flexible

Special: Iceberg / Moonbow / Sol

Passive A: Atk/Res Unity / Close Ward

Passive B: Mystic Boost / Quick Riposte

Passive C: Sparkling Boost+ / Rein Skills / Smoke Skills / Joint Drive Skills / Flexible

Sacred Seal: Kestrel Stance / Atk/Res Solo / Quick Riposte / Atk/Spd Solo 

• Eir’s refined Lyfjaberg offers an abundance of effects — massive in-combat stat enhancements, Guard, enemy follow-up denial, and further healing for herself and nearby allies — that altogether renders the princess pretty effective at defensive play, most notably against magic threats given her Resistance lean. This build capitalizes on precisely that and can be used either for general gameplay, or potentially to alleviate some of the pressure on her team’s main carries (though her inability to be Blessed highly discourages using her as the sole ranged tank).
• Her base Atk/Res Unity is simply phenomenal, removing any fear of having stat penalties or Panic interfering and instead allowing her to exploit them for potentially massive stat enhancements. The main reason to consider removing it would be to utilize Close Ward in conjunction with Mystic Boost to extend Eir’s anti-magic capabilities against dragons as well, though whether this is actually worth it depends on preference.
• Ranged fliers are unfortunately still quite lacking when it comes to defensive B skills, though Eir thankfully comes equipped with her ideal choice by default: Mystic Boost. This skill excels at further supplementing her healing potential to the point that she can very easily just use a damage-dealing Special without sacrificing durability. Quick Riposte deserves a mention, however, as it allows Eir to break through Impact effects, but it can be equipped as a Sacred Seal as well.
• Keeping Sparkling Boost+ is an option to maintain Eir’s supportive value amongst her teammates. That being said, given the combat-intensive nature of this build, it’s perfectly within your reach to replace it with a more selfish skill like your choice of Rein, Smoke, or Joint Drive.
• Lastly, beyond Quick Riposte, any stat-enhancing Sacred Seal will work wonderfully. It’s important to remember that refined Lyfjaberg requires that Eir maintain higher Speed than her foe to maintain its Impact and Guard effect active during the Enemy Phase, so prioritizing Speed boosts alongside either Attack or Resistance is recommended.