If you don't have Katya - Dawnwing yet but want to try her out, she is available as a Trial Operative in Story Mission SP5-1
Dawnwing is a good all-round operative - good damage, good mobility (and thus good survivability), but to get the best out of her requires very high investment.
Role: Main DPS
Frost Damage
Deals mostly skill damage
Fantastic mobility
Very high damage
Quite consistent damage
High mobility gives good survivability
Quite a simple damage rotation
You don't need to take your focus off the enemy
Never needs to manually reload
Her skill/dodge can phase through enemy barriers
You need to constantly spam her skill
Constant use of her skills means she has to constantly move
Really wants high investment
Very high investment ceiling
1. Hold your Standard Skill to create Crystal Vanes until you have at least 6 of them.
2. Shoot an enemy until the passive procs. 6 Crystal Vanes will damage the enemy, and 3 Crystal Vanes will be removed.
3. If in single-player content, and Dawnwing has 6 Crystal Vanes, use her Ult off-cooldown.
If in multi-player content, your first Ult is a DPS loss, so you may want to avoid using your ult in multi-player content unless you plan to use your ult a lot.
Repeat
Note 1: If a boss has an invulnerability phase, use her Standard Skill to get as many Crystal Vanes as possible up before its invulnerability wears off.
Note 2: If a boss has an invulnerability phase, shoot the boss until your Aurora Charge gauge is almost maxed, so your next shot triggers it.
Standard Skill
Tapping Dawnwing's Standard Skill causes her to dash in the direction she is moving in (or forward if she isn't moving) and create 1 Crystal Vane.
If you hold the skill down it will cause Katya to do two dashes, and create 3 Crystal Vanes. (whilst still using the same S-Energy as a single dash)
The two dashes don't have to be in the same direction - you can dash one way, dash the opposite way, and end up back where you started.
This is recommended and doesn't require much practice to do.
Further note that the dash (as well as Dawnwing's regular dodge) is more of a phase, and does allow her to go through most enemy-created barriers.
That Dawnwing's standard Skill moves her so much is what gives Dawnwing so much mobility.
Dawnwing can have a max of 12 Crystal Vanes at once.
Dawnwing's Standard Skill does also deal some PBAoE Frost damage when creating a Crystal Vane.
This isn't much damage, but it's something, and is good enough for clearing trash mobs.
Against bosses, staying near the boss so this PBAoE damage hits them will increase your damage a little.
You may wish to get Dawnwing to 12 Crystal Vanes before using a debuff (e.g. Celestial Swan), so that you don't need to create Crystal Vanes during the debuff and can just do damage to make the best use of the debuff as you can.
Note that some in-game effects treat the two parts of Dawnwing's Standard Skill dash as separate skills/effects
For example the effect "50% of S-Energy consumed when using a skill is converted into U-Energy" buff gives U-Energy for both the first and second dash
(Granting 4 and 3 U-Energy respectively) [If you only do one dash you only get the first lot of 4 U-Energy]
Passive Effect
Dawnwing has a gauge near the middle of the screen that fills.
This fills slowly when in combat, or quickly when shooting.
(Max is 100. Gain 10/s naturally, as well as 4 per shot hit.)
When full, the next shot Dawnwing fires will reset the gauge and trigger her Crystal Vanes - Up to 6 Crystal Vanes will fire at the shot enemy, dealing high Frost damage.
After proc'ing the passive, some Crystal Vanes disappear (how many disappear depend on how many you have. With 6 or more Vanes up, 3 Vanes will disappear)
Since a maximum of 6 vanes proc, having more than 6 vanes up doesn't increase Dawnwing's damage.
You can use periods of downtime (e.g. enemy invulnerability phases) to build vanes, so that you don't need to make them during combat and can focus on just on proc'ing the crystals rather than making them, because the crystal proc is where most of Dawnwing's damag comes from.
For each Crystal Vane that fires at an enemy, Dawnwing recovers 4 bullets.
With the max of 6 Crystal Vanes firing, this means Dawnwing recovers 4*6=24 bullets per proc.
Due to Dawnwings natural aurora regneration (10/s) means it actually takes her a little less than 24 bullets to proc her vanes, which recover 24 bullets.
This means that [provided you land your shots] Dawnwing never needs to manually reload.
Shooting an enemy builds the gauge, even if the enemy is invulnerable.
This allows you to build the gauge to full whilst an enemy is invulnerable so that when they become vulnerable again your next shot proc's Dawnwing's Crystal Vanes.
Note that in practice you don't need to worry about her Crystal Vanes - just use her standard skill after the vanes fire, and you'll always stay at or above 6.
Dawnwing will also use her standard skill automatically when switched in (This doesn't use any S-Energy or skill charges though)
This does create Crystal Vanes, but since it's her standard skill it does also cause her to move, which can make it a liability in certain situations.
Especially if you only move once and don't dash twice to end up back where you started.
Note that for Dawnwing to double-dash when switched in you need to hold her standard skill key (Default: E) down, not her swap-in key.
This does require some practice.
Ultimate Skill
Dawnwing's Ultimate Skill causes her to shoot a huge arrow at the target that deals Frost damage.
This also causes Dawnwing to use up to 6 Crystal Vanes (if you have them) to fire a ray at the target.
...this does mean that Dawnwing's Ultimate skill is basically her Standard Skill with an extra Frost Damage projectile on top.
Dawnwing's Ultimate Skill also restores all her standard skill charges, allowing you to immediately use your Standard Skill again.
This isn't actually needed with perfect play, but it is useful if you miss some shots and/or are running out of S-Energy due to using your Standard Skill to clear trash mobs.
In Single-Player content, time slows down when you use your Ultimate.
In Multi-player content time does not slow down, meaning that if you haven't disabled ultimate animations then Dawnwing's Ultimates are a DPS loss in multiplayer - it just takes too much time to activate for its damage - you're better off just using the standard damage rotation above (with her Standard Skill) instead.
You can disable ultimate skill animations in the options menu, and if you use Dawnwing in multiplayer content that is something you will very much want to do.
If you don't do that then again - I am not personally convinced her Ult is ever worth using in multiplayer - I think you're better off using her standard skill as normal instead.
The one exception is if you can pre-cast her ult, which can be tricky to pull off.
Aurora Sands
Her 5* weapon, and her best weapon.
Tornado
Her 4* event weapon. A bit more clunky in its buffs, but still good.
For weapon Parts just go with max ATK.
Use Vector squad - it was designed specifically for her and is her best choice.
For stats you want 10.0% ATK and +106 Alignment Index.
For the Special talent, you want 8.5% Frost Damage
Alignment gives her more ATK.
All 3 Logistics officers having max Alignment gives Dawnwing +19.08% ATK.
All other stats are either functionally useless for Dawnwing or literally useless for Dawnwing.
All of Dawnwing's Manifestations increase her damage by a notable amount.
This means that you ideally want Dawnwing to be at M5 for max damage.
If you don't want to invest that much into Dawnwing, you can stop at any point, but not getting to M5 will give Dawnwing notably reduced damage when compared to her at M5.
This is also why Dawnwing wants high investment - each of her Manifestations add a lot to her damage, and she ideally wants all of them.
Similarly, Dawnwings T5 weapon is also a large increase to her damage.
Most of Dawnwing's damage comes from her Crystal Vane procs, not from her shooting, meaning that ballistic buffs are not overly useful for Dawnwing.
Instead, Dawnwing wants skill damage buffs or debuffs to enemies damage resistances:
Vidya - Celestial Swan (and other resistance shredders)
Celestial Swan and other resistance shredders (Acacia - Kaguya, etc.) that reduce the enemies resistance help enemies take more damage.
If using Celestial Swan, make sure the other support isn't off element to the main DPS.
Tess - Phantasia
Per-shot Frost damage works out very well for Dawnwing, due to Dawnwing spending most of her time in combat shooting stuff with a high-RoF AR.
Phantais is also on-element to Dawnwing, allowing her to be used alongside Celestial Swan.
Marian - Riptide
Dawnwing's damage rotation is short, so it's easy for Riptide to swap in and maintain her buffs, which makes her good for Dawnwing.
Note that Riptide is off element to Dawnwing (Riptide deals chaos damage)
Enya - Exuvia
Continually shooting whilst wanting mostly skill damage buffs makes Exuvia a good support for Dawnwing, altohugh Exuvia is off-element to Dawnwing.
Eatchel - The Cub
Dawnwing's extreme mobility means she doesn't massively need Eatchel's healing buffs, but Eatchel's ATK buffs are still good.
Note that Tess - The Magician doesn't really work very well with Dawnwing, as Dawnwing's Ult is basically a slightly stronger version of her Standard Skill, and isn't a large enough dps increase to justify using an entire support operative to use her ult faster.
Similarly, again, Dawnwing's ballistic dps is a small percent of her damage, with most of her damage being from her Crystal Vane proc.
This means that ballistic supports like Nightglow aren't overly useful to her.
Similarly, since she never needs to reload, buffs to magazine capacity or reloading buffs (i.e.Fenny - Starshine) aren't useful either.
Overall, Dawnwing is a very capable operative if properly invested into.
Many of her attributes are a double-edged sword though
She has very high mobility, which gives good survivability, but needing to constantly move is annoying and can be a liability in some situations.
She can have extremely high DPS - but she needs a huge amount of investment to do it.
The downsides of Dawnwing are:
That you are required to use her Standard Skill very often to rebuild Crystal Vanes.
This does break flow somewhat, and means Dawnwing's damage might not align well with certain debuffs (e.g. Celestial Swan)
You may wish to get Dawnwing to 12 Crystal Vanes before using a debuff, so that you don't need to create Crystal Vanes during the debuff and can just do damage
to make the best use of the debuff as you can.
That you are required to use her Standard Skill very often to rebuild Crystal Vanes, thus moving you.
This makes Dawnwing more difficult to use with Quiet Quitter, as it's more difficult to stay in the healing PBAoE.
Quiet Quitter is the early-game healer, so Dawnwing not synergizing well with her can make Dawnwing hard for very new players to use.
Quitter isn't useful/used at endgame, and endgame players will have Eatchel anyway, so this only affects new players though.
You'll get used to it eventually, but if you don't play Dawnwing much and don't get used to her movement it then it can feel annoying or difficult.
You also can't play Dawnwing as a stationary operative - she has to move constantly.
That you are required to use her Standard Skill to build Crystal Vanes.
This means that Dawnwing has an inevitable wait before she can start dealing high damage.
Her first Ultimate is a large DPS loss in multiplayer, which does reduce her effective damage somewhat versus operatives that can use their Ultimate.
Dawnwing wants high investment.
All her Manifestations add a good amount to her DPS, and her 5* weapon is a huge damage bonus too.
This makes Dawnwing one of the more expensive operatives to use at high investment levels.
Her Standard Skill does deal some AoE damage, but Dawnwing is a primarily single-target damage operative.
You need lots of buffs/investment to get Dawnwing to the point where her Standard Skill can clear mobs pretty easily... although it is possible.
Her downsides are generally minor, and with some investment Dawnwing is a strong operative against groups of trash mobs and bosses alike