Ether

A Burst 1 Electric Shotgun SR Defender Nikke who gives low-HP allies a shield and Damage Taken reduction, and debuffs high-DEF enemies during Full Burst.
She is rarely a main pick in story, bosses, Raids, or Arena.
Her SR tier and limited buffs and firepower make her investment priority low.

She reduces damage taken by the single ally with the lowest HP, and using her Burst Skill gives the three lowest-HP allies a shield based on her final Max HP. Using her skill deals damage to the three enemies with the highest DEF, and while Full Burst continues, she lowers the DEF of one of them.

Keep up Shotgun fire at close range and time her reloads.
While Full Burst continues, apply the DEF debuff with Prognostic Response Experiment2.
Leave her on auto by default, and only adjust her position when she needs to stay close.

There is little evidence of her being paired in the same squad in the recent meta.

Close-range accuracy matters for a Shotgun, so prioritize the Assault Cube and Onslaught Cube. Cover survival with the Tempering Cube. If Harmony Cube levels differ a lot, use the higher-level cube before the ranking.

Her shield scales with final Max HP, so prioritize DEF and HP lines, and set Elemental Advantage damage and ATK for her own firepower later.

At SR tier, unless she is a meta core unit, save skill books and only raise Corrosive Bullets1, Prognostic Response Experiment2, and Colossal Single CellB to 4 when you use her. Maxing to 10 gives little return for the investment.

She is rarely seen in top Solo Raid lineups. She more often fills Burst 1 CDR, tank, or supporter slots.

She can give low-HP allies a shield and Damage Taken reduction.
While Full Burst continues, she lowers the DEF of high-DEF enemies.
She deals skill damage to three high-DEF enemies.

At SR tier, her buff and shield values are low by meta standards.
As a Shotgun, her debuff and protection contributions break off depending on range and reload.
Her own firepower is small, so she is rarely a main pick.