If you don't have Vidya - Celestial Swan yet but want to try her out, she is available as a Trial Operative in Story Mission 15A-8
Celestial Swan is an extremely strong support operative who works with all DPS operatives, however if using Celestial Swan as a support then the teams other support operative should either not deal damage or type-match the DPS, which can make teambuilding difficult for certain operatives.
Role: Support: DEF and resistance debuffer
Deals Chaos Damage
Deals basically no damage
(Although deals mostly skill damage)
Mobility is moderate
Incredibly strong as a support operative
Extremely easy to use as a support operative
Extremely terrible as a DPS.
Forces your other support to element-match your main DPS, which can making teambuilding difficult
How to use Vidya - Celestial Swan
1. Use Celestial Swan's ult immediately as the fight starts
2. Spam her Support Skill off-cooldown
If she has her 5* weapon, her support skill will last indefinitely until the target dies, so you'll only need to apply it to your target once.
That's it.
Standard Skill
Vidya throws out a holographic landmine. (Holographic = They project Celestial Swans model)
The landmines detonate when an enemy get close. Vidya can also shoot a mine to detonate it prematurely.
Every 1.5s these are out, these increase in damage and AoE, maxing after 3.0s deployed.
Tapping the Standard Skill key deploys the landmine in front of Vidya. Holding it causes Vidya to throw the landmine at the targeted location.
Vidya has quite a good throwing arm ( don't ask how she got it ) and can actually throw them quite far.
Vidya can have up to 5 of these landmines up at a time. Deploying more beyond that causes the oldest to be detonated.
Whilst this skill can be quite fun, it can also be clunky and tedious, and its sutsained DPS is poor.
Ultimate Skill
Celestial Swan marks the target as a Prime Suspect.
If that enemies HP gets below a certain amount (determined by Celestial Swan's U-Energy) then Vidya immediately executes them.
(Mechanically, Vidya deals True DMG to the target - meaning it ignores things like DEF and resistances - the target just takes its current HP as damage, thus dying.)
In practice, the HP threshold for this to trigger is so low it's basically useless.
Note that Celestial Swans ult has infinite duration.
Support Skill
Vidya's Support Skill causes the targeted enemy to reduce the targets DEF.
In addition, damaging the target causes them to decrease their resistance to the type of damage they took.
This stacks up to 5 times, and the target can gain 1 stack every 2 seconds, however with a Neuronic Vidya can immediately inflict 4 stacks, meaning she can stack the max debuff pretty much instantly.
The DEF debuff is 16%, 28% with M1, or 29.6% with M4.
If Celestial Swan' has M5, then if her support skill is used on the same target as her ult, that target also gains 8% Increased DMG Taken, which is extremely strong.
Each stack of the debuff grants 5% ResPen, for 25% total, or 35% with M2.
With M3 max stacks of the debuff also grant a 15% ATK buff to all other operatives.
With M4 the debuff is increased to 5.5% per stack, for 38.5% ResPen
This skill uses S-Energy continuously, and Vidya doesn't recover S-Energy whilst it's active.
It uses 1 S-Energy every 0.2s, for 5/s, meaning it has an uptime of 10 seconds.
This skill has a 5s cooldown after it ends. After the cooldown is over, Vidya recovers 50 S-Energy (which is her max), so she can immediately use it again.
This means this skill has a 10 second duration and a 5 second cooldown, for 66.6% total uptime.
Also yes, all of Celestial Swan's Manifestations buff her Support Skill.
Most critically though, is that Celestial Swans Support Skill only provides a damage reduction to one damage type at any given time.
If an enemy is damaged by a new damage type, then it loses its resistance reduction to all its previous type
This means that you can't use multiple different damage types and have Celestial Swan buff all of them.
In practice this means that if you are using Celestial Swan, then you will want your other support operative to either not deal damage, or to deal the same type of damage as your main DPS.
If using Celestial Swan, then having your other support operative and your DPS not type-match is a very significant DPS loss compared to having them type-match, to the extent that if the other support and the dps don't type-match then you're usually better off using another support instead of Celestial Swan, or swapping the other support for a weaker support that does work with Celestial Swan.
This can make teambuilding with Celestial Swan quite complicated.
Starlit Truth
Her 5* weapon, and her best weapon.
Gives Vidya a nice ATK buff, a nice damage buff to the whole squad.
If using her Support Skill while below 20 S-Energy, Vidya gains 1 S-Energy every 0.2s, which is the exact same rate she uses it at.
This means that Starlit Truth gives Celestial Swan infinite duration for her Support Skill.
This is actually a very nice QoL feature and not having to spam her skill so often is very nice.
When dealing damage during her Support Skill, the weapon also increases damage of that type, and increases the damage enemies take to that type.
Gearlock
Her 4* event weapon.
This gives her 10 S-Energy when her S-Energy falls below 20, once per skill use. This increases the duration of her support skill by 2s, for 70.5% uptime.
It also gives a nice damage buff to the whole squad, which is nice.
For weapon Parts just go with ATK.
Use Nebula squad - it was designed specifically for her and is her best choice.
For stats you want +106 Alignment Index and +10.0% ATK.
For the Special talent, it doesn't matter - all possible stats are literally useless.
Alignment Index gives other operatives an extra ATK buff based on Vidya's ATK (1% ATK per 100 Alignment. Not much, but being a passive buff with 100% uptime makes it good.)
ATK is useful for buffing Vidya's passive Alignment buff, as well as her ultimate.
ATK is a bit worse for Vidya than Alignment, but it's still her second best stat.
Since Celestial Swan is a support operative, defensive things like Max HP and DEF are useless to her.
Heal Bonus, Aux Unit Strength, and Shield Construction Efficiency are literally useless.
Being a support operative that never deals damage, crit mods are literally useless for Celestial Swan.
(and she deals mostly skill damage on-field anyway, and skills can't crit)
Since she recovers max S-Energy after her Standard Skill comes off-cooldown, and she can't recover S-Energy whilst it's active, S-Energy mods are useless to her.
Since Celestial Swan doesn't really recover U-Energy, U-Energy Recovery isn't a useful stat for her logistics to have.
Skill Haste is a cope stat if not using her 5* weapon - Celestial Swan has a very high uptime on her support skill anyway, and even higher with her 4* weapon, but Skill Haste will give her more uptime, although it's not a large increase to her uptime.
Since her 5* weapon gives her Support Skill infinite duration, Skill Haste is literally useless if using her 5* weapon.
Similarly, since you'll hopefully get her 5* weapon eventually anyway, getting Skill Haste for her 4* weapon just means she'll need to re-roll later, which is not ideal.
For the Special Talent, being an off-field Support Operative who doesn't deal damage makes Celestial Swan incapable of benefitting from any Special Talent in any way.
This means that you can ignore the Special Talent entirely.
You can potentially go for +8.5% Chaos Damage just in case Celestial Swan should ever be on-field for some reason (such as wanting to test the games physics engine...) but if you're using Celestial Swan as your main dps for actual damage then something's already gone very wrong. Just save the Special Talent re-rolls for another operative.
Celestial Swan is an extremely strong support, and works very well for literally all DPS operatives.
Using Celestial Swan means that you want your other Support Operative to deal the same type of damage as your DPS or to not deal damage at all, but beyond that restriction Celestial Swan doesn't limit your squad in any way.
This type-matching restriction does mean that Celestial Swan does work much better for some operatives than others.
For example Clarina + Eatchel + Celestial Swan works perfectly, and is Clarina's ideal team.
Alternatively: For Bubu - The Geomancer, since Bubu doesn't really have any ideal Thermal supports, she is limited to off-element supports (like Yao - Nightglow) and not using Celestial Swan, or alternatively using Celestial Swan with a weaker second support like Eatchel or Fenny - Starshine.