Seiros

Weapon: Aurora Breath

Assist: Positional Assist / No Assist / Flexible

Special: Glimmer / Moonbow / Iceberg / Glacies

Passive A: Mirror Impact / Distant Counter 

Passive B: Dragon Wall / Wings of Mercy / Lull Atk/Res

Passive C: Wings of Light / Time’s Pulse / Drive Skills / Smoke Skills / Flexible

Sacred Seal: Atk/Res Bond / Hardy Bearing / Mirror Strike / Death Blow / Quickened Pulse

• Given her status as an Anima Mythical Hero, a build dedicated to Seiros’ performance within the context of Aether Raids Defense is only natural—and thankfully, her skill set enables her to make an overall meaningful contribution to one’s defense team. An Attack Asset is preferable over her other options to maximize her damage, but boosting one of her defensive stats may also work if aiming to use the saint as more of a wall. 
  • It’s worth noting that although potential alterations are always welcome to best fine-tune Seiros to serve your particular team, much of this set consists of her innate kit as it is already quite effective. 
• Seiros’ ideal choice of Assist is tricky here and will largely be case-dependent given that it is necessary to account for the way in which the AI prioritizes turn order—or she can go without one at all to avoid potential mishaps. 
• For her Special, those with low cooldowns—namely, Glimmer and Moonbow—work well and can potentially activate in a single round when she initiates combat, with Glimmer pairing especially well with her high offensive ceiling. For those using Seiros within an Infantry Pulse setup, using Iceberg or Glacies if enough charges are available allows for massive damage as they leverage her monstrous Resistance.
• Her base Mirror Impact is an excellent candidate for her A slot for a more aggressive approach to Seiros, granting her a substantial Attack and Resistance boost (which also enhances the strength of Dragon Wall’s damage reduction) and the ability to  deny enemy follow-up attacks. However, Seiros can also opt for Distant Counter if using her as a wall to punish Player Phase strategies and make initiating against her much more dangerous. 
• Dragon Wall is a highly effective B skill choice to further augment Seiros’ fantastic durability, directly reducing her foe’s damage based on the difference between their Resistance; this lends itself well to most playstyles. Wings of Mercy is a potential alternative should one want to highlight Seiros’ damage ceiling and expand her mobility, or Lull Atk/Res to break through enemy bonuses.
• Like most other units, Seiros isn’t too attached to any particular C skill, but standouts include her exclusive Wings of Light to enhance the combat of other Mythics, Time’s Pulse to hasten her Special (especially in Infantry Pulse setups), and Smoke skills. For her Sacred Seal, anything that enhances her key stats—ideally in the form of a Bond or Blow skill—works well, or Hardy Bearing to check Vantage units.

Weapon: Aurora Breath

Assist: Positional Assist / Flexible

Special: Sol / Noontime

Passive A: Distant Counter

Passive B: Dragon Wall / Dragon’s Ire / Special Spiral

Passive C: Smoke Skills / Time’s Pulse / Wings of Light / Flexible

Sacred Seal: Quick Riposte / Mirror Stance / Atk/Def Solo / Fierce Stance 

• Aurora Breath’s massive Defense and Resistance boost—alongside its negation of her foe’s follow-up attack—during the Enemy Phase complement Seiros’ base statline incredibly well, and make running a purely defensive set a rather attractive option for general usage outside Aether Raids. Besides a +ATK IV, taking +DEF or +RES also work to reduce the damage she takes even more. 
• Taking a healing Special is highly recommended to supplement her tanking ability with a consistent source of sustain, allowing her to easily maintain high levels of HP. Sol is generally ideal as the activation of its timing will tend to work out the best with most skills, but Noontime is a potential option if New Year Velouria, Infantry Breath, or Time’s Pulse is available for immediate activations on each counterattack. 
• Distant Counter is crucial to maximize the legendary saint’s versatility through the ability to counterattack regardless of range, allowing her to check a much wider breadth of foes. 
• Seiros has a few choices for her B slot, with the primary choices being Dragon Wall and Dragon’s Ire; the former offers much greater survivability through its damage reduction, but the latter is essentially a significantly stronger Quick Riposte that innately breaks through Impact-esque skills. Special Spiral is also an option to activate Sol on every counterattack in an OHKO-oriented build. 
• Smoke skills innately benefit a defensive playstyle wonderfully and thus make for a welcome addition to Seiros’ build here, though she’ll only really get use out of Atk Smoke or Res Smoke. Time’s Pulse is also a consideration if aiming to use Noontime, or her Wings of Light if using other Mythics on the team. The Quick Riposte Sacred Seal (if not using Dragon’s Ire) or any that build on her key stats work well here. 

Weapon: Aurora Breath

Assist: Positional Assist / Flexible

Special: Iceberg / Glacies 

Passive A: Mirror Impact 

Passive B: Null Follow-Up / Lull Atk/Res / Dragon Wall

Passive C: Smoke Skills / Joint Drive Skills / Time’s Pulse / Flexible

Sacred Seal: Heavy Blade / Mirror Strike / Death Blow / Atk/Def Solo 

• Alternatively, Seiros can focus on the substantial Attack boost and guaranteed follow-up she obtains upon initiating and invest fully into her Player Phase performance. Since the focus here will be ramping up her damage as much as possible, a +ATK IV is preferred over all else. 
• Iceberg is a strong Special choice that combos well with Aurora Breath’s effect and the Heavy Blade Sacred Seal, enabling Seiros to potentially activate it in every engagement; this allows for strong and consistent damage. Should greater burst be preferred, her native Glacies is an option but its activation rate is rather inconsistent. 
• Mirror Impact once again prevails as Seiros’ ideal A skill, aiding her offensive prowess—it even helps improve her Iceberg/Glacies damage—while offering a solid degree of safety when initiating. Her B skill should similarly assist the power of her initiations, with some choices being Null Follow-Up to ensure her follow-up attack and Lull Atk/Res to break through enemy bonuses. Dragon Wall may be useful to safeguard her longevity. 
• Once again, Seiros’ choice of C slot isn’t particularly important and can be filled by pretty much anything that benefits her team, such as her default Wings of Light. That being said, Smoke skills are always solid when provided with refresher support and Time’s Pulse assists her damage by hastening her Special activation. Any Attack-boosting Sacred Seal available is recommended.