If you don't have her yet but want to try her out, she is available as a Trial Operative in Story Mission SP5-8
Nerida is a strong and mobile operative but she really really needs Marian - Riptide as her side as her Sub-DPS, and for a large part of her rotation she and Marian basically have to stay still for a little bit.
Role: Main DPS
Chaos Damage
Deals entirely skill damage
Mobility:
During ult: Nerida: Poor
Marian - Riptide: Decent
Otherwise: Incredible
High DPS
Great Mobility during standard skill
Standard Skill can hit numerous targets
(Even at long range)
Special damage mechanic can bypass invuln
Poor mobility during ult
Constantly moving during standard skill can get annoying, especially in confined spaces
Vastly worse if not paired with Marian - Riptide
Seriously: Don't play Styx if not paired with Riptide
Spends almost zero time in combat actually visible
(So purchased outfits aren't good value)
1. Use Nerida's Standard Skill until both Nerida's Wail Charge gauge is full and Marian - Riptide is at full Tidesong.
2. Use Nerida's ult
3. Immediately hold Nerida's standard skill to detonate all her ribbons
4. Swap Riptide in and magdump as fast as she can
5. Immediately swap Nerida back in via her support skill
Repeat
Ideally you do steps 2-5 quickly enough that Nerida's Support Skill can hit the enemy before her ult runs out.
Having Riptide's RoF boost from her M1 helps with this.
Standing near the enemy can help with Nerida's Support Skill hitting the enemy before her ult runs out.
Standard Attack
Nerida shoots her gun.
If you ever get to the point where Nerida is actually shooting enemies with her gun then you f**ked up a long time ago.
Passive Effect
Whenever Nerida deals skill damage while equipped with a Chaos weapon (i.e. hopefully always) her damage also inflicts an additional 80% of the damage inflicted as "Wrath Haunt", which deals DoT damage.
If an enemies HP is less than the Wraith Haunt, then the Wraith Haunt is very quickly converted to damage, basically acting as a finisher for weak enemies.
Standard Skill
Tapping her standard skill causes Nerida to create a Phantom every 0.5s that fires ribbons at several targets in front of her, dealing Chaos damage.
Each phantom she creates counts as a standard skill use, so Nerida uses a standard skill every 0.5s.
This gives her Wail Charge, which is used for her ult. It also gives her a little U-Energy.
Whilst using her standard skill, Nerida can't be interrupted, but also can't regen S-Energy.
She also quickly moves around in the targeted direction.
Holding her standard skill causes Nerida to consume all her Wail Charge to deal damage to enemies in front of her based on how much Wail Charge she used.
This also recovers all her S-Energy.
Ultimate Skill
Nerida creates a "Truth-Seer plasma jellyfish" (I.e. big AoE thingy) which causes Wraith Haunt to be increase from 0.8x to 1.8x but not cause DoT damage, as well as causing Wraith Haunt to be inflicted by any operatives Chaos Skill DMG, not just Nerida's.
With a Neuronic, Nerida using her ult also causes all previously inflicted damage to be increased to the 1.8x multiplier.
When Truth-Seer ends, all the Wraith Haunt is immediately converted to damage.
With a Neuronic, any target in Nerida's ult that has Wraith Haunt greater than its current HP is immediately defeated.
This can bypass invuln.
Nerida's ult lasts very slightly longer than it takes for Nerida to hold her standard skill, swap Marian in and magdump, and then swap Nerida in via her support skill.
Support Skill
Nerida fires ribbons in front of her, dealing chaos damage.
This also swaps Nerida in.
Shadow Surge
Her 5*, and her best weapon.
Web Snare
Her signature 4*, which gives her a nice Chaos DMG and ATK boost.
For Weapon Parts just go max ATK.
Use Sidhe squad - it was designed specifically for her and is her best choice.
This gives Styx a very large 65% Skill DMG boost (doubled during her ult) which makes it amongst the largest dps-increases from a logistics squad in the game.
For stats you want +10.0% ATK and +106 Alignment Index.
For the Special talent, you want 8.5% Chaos Damage
Alignment Index gives Nerida more ATK, which is very useful.
Nerida recovers her S-Energy at the end of her rotation, and hence S-Energy regen is useless to her.
Nerida's standard skill generates enough U-Energy for her ult, so U-Energy regen is useless to her.
Since skill dmg can't crit, and Nerida only deals skill dmg, skill dmg mods are useless to her.
M1 increases Nerida's damage by 25%
M2 causes Nerida's standard skills to bypass 15% of the targets chaos res.
This isn't quite a 15% damage boost (especially as it doesn't buff Riptide), but it's still nice.
M3 causes Nerida to ignore 20% of a targets DEF when equipped with a Chaos Weapon (I.e. hopefully always)
M4 increases the skill level and damage of Nerida's standard skill
M5 increases the entire squad's ATK by 8% of Nerida's ATK during her ult.
This is good for Nerida, but also good for Marian - Riptide.
If you want efficiency (good damage with minimal investment), then M3 is a good stopping point.
Marian - Riptide
In case it wasn't obvious by-now, Marian Riptide is Nerida's best partner by-far.
Styx Envoy was basically designed around having Riptide as her Sub-DPS, and Nerida performs vastly worse if Riptide isn't by her side.
If you don't have or otherwise can't use Marian - Riptide alongside Nerida, then I recommend that you do not use Nerida.
Alongside Riptide, most of the usual skill dmg supports work well:
Vidya - Celestial Swan
DEF and Resistance shredding are excellent for Nerida
Since both Nerida and Riptide both deal Chaos Damage, there's no worry about losing Celestial Swans buffs by being off-element.
Siris - Freefin
Freefin provides strong skill damage buffs, although Nerida can't make use of Freefin's Wavehunt thermal skill damage buff.
Eatchel - The Cub
A nice passive ATK buff.
Acacia - Kaguya is fine for resistance debuffing if Celestial Swan is busy that week.
Mauxir - Shadow Ka
More damage, and more Chaos Skill DMG is very nice.
Chenxing - The Observer
Skill DMG and Standard Skill DMG buffs are great for Nerida.