Echidna

Preferred IV: +RES / -HP

• Increasing Echidna’s Resistance is important for Aether Raids to help mitigate the onslaught of magical damage, including against AoE Specials from units like Ophelia.

Weapon: Slaying Axe (+Res/+Atk/+Spd)

• A +Res refine is ideal for maximizing Echidna’s magical bulk, but a +Atk or +Spd refine is acceptable if she has enough Resistance (such as from gaining additional Resistance from Mythic hero blessings).

Assist: Reposition

Special: Noontime

• Noontime’s cooldown is reduced to 1 with a Slaying Axe, allowing Echidna to recover some HP after being attacked. This sustain greatly increases her survivability.

Passive A: Distant Counter

• Being able to counter ranged threats is vitally important in Aether Raids, where the majority of huge threats are ranged.

Passive B: Null C-Disrupt / Null Follow-Up

• Both Null C-Disrupt and Null Follow-Up are incredibly powerful skills that allow infantry units to completely shut down otherwise dangerous threats. The choice between the two is entirely up to player preference and availability.

Passive C: Pulse Smoke / Atk Smoke

• Pulse Smoke is an incredibly powerful skill as it can single-handedly shut down Infantry Pulse-based defense teams in Aether Raids.

• If Pulse Smoke is unavailable, then Atk Smoke is a good budget option for increasing Echidna’s overall survivability.

Sacred Seal: Swift Stance / Atk Smoke / Quick Riposte

• Swift Stance is a fantastic Seal, as Speed and Resistance are both key stats that Echidna needs, particularly for Aether Raids.

• Atk Smoke is a decent alternative if not using it as a C skill.

• Quick Riposte isn’t particularly necessary with the right team support, but can be useful to help Echidna secure doubles against faster enemies.

Preferred IV: +ATK or +SPD / -HP

• Echidna is primarily geared toward offense, so maximizing her Attack or Speed is ideal for her offensive potential.

Weapon: Firesweep Axe+ / Slaying Axe+(+Spd) 

• Firesweep Axe is a strong option for Echidna as negating enemy counterattacks makes it very safe for her to attack most opponents.

• A Slaying Axe is a good alternative option as it enables alternative build paths such as maximizing damage output with repeated Special activations or utilizing Galeforce.

Assist: Reposition

Special: Moonbow / Galeforce

• Moonbow is a strong option for both a Firesweep Axe and Slaying Axe set, mostly due to its low cooldown and fairly consistent damage. Utilizing either the Flashing Blade or Heavy Blade Seals can allow Echidna to charge it immediately, while Quickened Pulse with a Slaying Axe can allow her to easily activate twice in one combat.

• Alternatively, Echidna can utilize Galeforce with a Slaying Axe and either the Flashing Blade or Heavy Blade Seal. 

Passive A: Swift Sparrow (2 or 3) / Fury (3 or 4)

• Pretty much any offensive stat boosting skill will work here. Swift Sparrow and Fury are both excellent choices (and relatively budget-friendly, aside from their 300 SP forms). 

Passive B: Lull Spd/Def / Lull Atk/Def / Null Follow-Up / Wrath

• Lull Spd/Def or Lull Atk/Def are both good options for increasing Echidna’s damage output, regardless of weapon. The Speed and Attack debuff portions are both helpful for helping her maintain Flashing Blade/Heavy Blade active as well. 

• Null Follow-Up is also a strong option as it prevents Echidna from getting her damage output shut down by skill that negate doubles, such as Wary Fighter or Axebreaker.

• Wrath is also a decent option, particularly if paired with a Slaying Axe, Moonbow, and the Quickened Pulse Seal to maximize Echidna’s Special damage.

Passive C: Odd Spd Wave / Flexible

• Echidna’s C slot isn’t particularly important for this build, but a self-buff like Odd Spd Wave can help supplement her damage output.

Sacred Seal: Flashing Blade / Heavy Blade / Quickened Pulse

• Flashing Blade or Heavy Blade are important to accelerate Echidna’s Special charge generation; the choice between the two is mostly up to preference.

• Alternatively, the Quickened Pulse Seal can greatly benefit Echidna’s first combat performance by allowing her to immediately activate her Special, or even activate it twice (with a Slaying Axe and Moonbow).