Siris - Freefin

Siris - Freefin is not currently available as a Trial Operative in any story mission, so if you don't have her the only way to try her is to wait for her banner so she has a trial.

Freefin is an excellent skill-damage buffer, who works best at buffing thermal damage operatives, but works well with any skill-damage operative.
Freefin is an ok dps but isn't great, and the Sub-DPS role provided by her ult is difficult to fit onto a team, making her ult very weak for the energy required to use it, and it doesn't fit well alongside any main dps operative.

TL:DR:

How to use Siris - Freefin

As a support operative: Use her Support Skill.
It ideally shouldn't, but if her Support Skill does run out, re-apply it again off-cooldown.

As a weak DPS: Use her standard Skill to get on her jetboard and enter Flowride state
Whilst on her jetboard, use her attack to deal PBAoE damage and charge her Swell Gauge.
If her Swell gauge is full, use her Standard Skill to deal strong PBAoE damage (This is where most of her damage comes from)
If her ult is ready, use it to deal damage and get on her jetboard to enter Flowride state, and then gain Swell Gauge at a higher rate.

How to build Siris - Freefin

Weapon: Splash Glider is her ideal weapon, but if you don't have that then use Ancient Nautilus
Weapon Parts: Max HP
Logistics Squad: Sprout
Basic Talent: +10.0% Max HP
+106 Alignment Index
Special Talent: +8.5% Thermal Damage, although this has such little effect it's not really worth the investment to get it even for min-maxing whales doing endgame content.
Works with: Any operative that deals Skill damage.
Works slightly better with thermal operatives, but the difference is small.
Works with Celestial Swan, even for non-thermal dps operatives.

Specifics:

The Basics

Role: Support
Deals Thermal Damage
Deals entirely Skill dmg
Mobility is incredible
Can generate quite a lot shield during her ult

Advantages

Logistics provide a very good 30% skill damage buff that is universally useful for skill-dmg operatives
Support skill gives strong support buffs, and can be used by most skill damage operatives
Works well with Celestial Swan, even for operatives that don't deal thermal damage
Incredible mobility
Incredible mobility can give good survivability
Extremely strong dps for a support

Disadvantages

Mediocre DPS on her own
PBAoE only - no long-range damage at all
PBAoE + no healing = survivability can be poor
If used as a support, her ultimate is always terrible and is never worth using

Standard Skill

Using her standard skill causes Siris to ride her jetboard around, which the game calls her being in the "Flowride" state.
Whilst riding she doesn't naturally recover S-Energy recovery, but she gains 5 S-Energy each time she hits an enemy.
She also loses 5 S-Energy each second to increase her speed by 20%.
This is an additive buff, not multiplicative, but either way it's not something that actually makes any difference to how she is played.

Whilst in Flowride, Siris can't shoot, but instead does a "Surfer Swirl" that deals damage to up to 4 nearby enemies and granting some U-Energy.
With her Neuronic, dealing damage deals 5 S-Energy, which is good for sustain.
This also grants Siris 15 Swell Gauge per target hit.
Siris has a maximum Swell Gauge of 100.
Using her standard skill again will do a "Tidal Strike" which will use all Swell Gauge to deal PBAoE damage, with more damage the more Swell Gauge she uses.
With her Neuronic, Siris restores 25 S-Energy with her Tidal Strike.
With her other Neuronic, using Tidal Strike at the max of 100 Swell Gauge then it deals +20% Final DMG.
Her Tidal Strikes are where the vast majority of Freefin's damage comes from.

Using a Tidal Strike while at max Swell Gauge, then she doesn't exit Flowride and resets her standard skill cooldown.
If Freefin doesn't have max Swell Gauge when using Tidal Strike, then she exits Flowride.
Dodging also exits Flowride.

The damage dealt by this skill scales with Siris' Max HP, not her ATK.

In essence, use her standard skill to enter Freeflow, and then once in Freeflow use her Surfer Swirl (i.e. LMB attack) until her Swell Gauge is full, and then use her standard skill to cast a Tidal Strike.

Ultimate Skill

Siris creates a whirlpool that deals AoE damage up to 10 times and knocks targets up into the air.
The whirlpool then explodes, dealing Thermal damage and causing Siris to enter the Freeflow state of her Standard Skill.

After using her ult, Freefin enters "Tsunami" state for 12s, which gives her an additional 3 Swell Gauge every 0.1s.
This means she gains 30 Swell Gauge every second, or 360 Swell Gauge total, which is enough for 3.6 fully-charged casts of her standard skill.
If used at max Swell Gauge, Freefins standard skill detonation instantly recharges the standard skill, allowing it to be quickly spammed.
This means that if you don't wait for her Swell Gauge to be full before unleashing her standard skill, then it will go on cooldown, which will waste a lot of the Tsunami state's Swell Gauge generation.

Freefin also grants the entire squad a shield whilst she is in Tsunami state. The shield is removed when Tsunami ends.
With her Neuronic, hitting enemies with her standard skills Tidal Strike generates "Gleamscale" that you can collect for more shield.

With her Neuronic, dealing damage with her standard skills tidal strike extends Tsunami, up to a max total duration of 18 seconds.

Note that Freefins ult uses 60 U-Energy.
This will be important when discussing her relationship with Fenny - Pureheart in the teammates section later on.

TL:DR: Her ult deals PBAoE damage, causing her to enter her standard skill state and charge it very quickly.
After using her ult, make sure her Swell Gauge is full before using her standard skill.

Passive Effect

If Freefin has a Thermal weapon equipped, then whenever the deployed operatives skill hits a target, Freefin grants them 3 Freetide stacks, gained at most every 0.5s.

Each stack of Freetide gives +0.25% Skill Damage, plus 0.1% per 100 Alignment Index.

If an operative doesn't gain a stack for 1 second, then they instead lose a stack of Freetide.

In essence, operatives that can frequently damage enemies with their skills get a nice skill damage buff from having Freefin on the team.

The little fish on the middle-left of the screen shows you how many Freetide stacks you have.

Support Skill

Freefin deals Thermal Damage to the target, and also decreases its ATK by 10% for 5s.
Given that her support skill has a 5s cooldown, this can have essentially 100% uptime.
With her Neuronic, an operative with Wavehunt also re-applies the -10% ATK debuff, allowing it basically 100% uptime even without spamming her support skill

Freefin's Support Skill also gives the deployed operative 20 Freetide stacks and 5 Wavehunt stacks.

Wavehunt stacks increase Thermal skill damage by 0.6% per stacks.
Having at least 10 stacks also gives an ATK boost of 0.6% of Freefin's Max HP. (Maybe 250 ATK with low investment. Maybe 300-350 with high investment.)
Having any Wavehunt stacks means that Freetide stacks don't disappear, allowing operatives to stay at max Freetide stacks for a strong skill damage bonus.
Having any Wavehunt also generates 3 additional Wavehunt stacks when dealing skill damage, up to every 0.5s, up to a max of 20 stacks.
If Freefin has a Thermal weapon and her Neuronic, then she also gives an extra 2 Wavehunt each second for 5s after using her support skill, for 10 total extra Wavehunt.
If a new stack isn't added every second, one stack is removed instead.
All stacks are lost when leaving the field.

Each Freetide Stack grants 0.25-1% Skill Damage (dpending on her Deiwos), plus 0.1% per 100 Alignment Index.
For the usual max of 618 Alignment Index, this gives 0.868% Skill Damage per Freetide stack.
For the 20 stacks her Support Skill gives and allows her to maintain, this is between 5% and 32.36% Skill Damage, depending on how much Alignment Index and Deiwos she has.

This means that using Freefins Support Skill grants an immediate Skill Damage boost, and a stacking Thermal Skill Damage Boost that increases over time up to a decent maximum, provided you regularly deal skill damage.

The TL:DR is that you can and should just use her support skill, and provided you are dealing skill damage decently often, Freefin's buffs will just maintain themselves without needing to re-cast it.
If your dps doesn't deal skill damage often enough, then Freefin's buffs will eventually expire, in which case you can just spam it whenever it comes off-cooldown,

Weapon

Splash Glider
Gives 21-35% Skill DMG whilst Freefin is off the field. After using Freefin's support skill, Freefin also gives the deployed operative a +15-25% ATK buff.
Whilst both effects are active, enemies damaged by the operatives also take 12-20% more skill damage
It gives Siris herself a 21-35% thermal skill damage buff whilst she's on the field.
It also gives 18-30% Max HP.
Ancient Nautilus
Gives a +24-40% Skill DMG bonus after using Siris' support skill, which lasts until Siris' is deployed to the field, which is a very nice support buff for a 4* weapon.
It also gives 12-20% Max HP.

Her weapons aren't very strong for her own damage, but they are excellent for supporting other operatives, which is her main role.
They also only give generic skill damage and ATK buffs, meaning she is useful for non-thermal operatives just fine.

For weapon parts Freefin wants Max HP.

Logistics

Use Libra squad - it was designed specifically for her and is her best choice.

If you got Freefin for free as part of her initial release, then she will have come with a full set of Libra squad logistics.
As usual for free logistics officers, these have their basic talent stats set to the correct stats at around 70% of max stats, and cannot be rerolled.
Their 3rd stat (Special Talent) is still random and can be re-rolled as usual.
(Although you shouldn't waste re-rolls on them, since their basic talents being fixed means they can never be made perfect).

Libra squad provides the entire team with a 30% Skill DMG buff whilst Freefin is off-field, which is a nice buff.
Libra also gives a +25% ATK buff the the deployed operative with Freetide and Wavehunt, which is a strong buff whils Freefin's support skill is active.
Siris also gains 3 extra Freetide each second whilst deployed, although as she's primarily a support that's not the most useful buff.

For stats you want +10.0% Max HP and +106 Alignment Index.
For the Special talent, you ideally want +8.5% Thermal Damage, but since you should ideally maintain her support buff indefinitely, Freefin ideally only deals damage once per fight, making the Thermal damage buff basically useless.
+Thermal damage is nice to have as her 3rd stat, but don't waste re-roll tokens to get it.

Since she ideally doesn't need to use her support skill more than once per fight, Skill Haste is useless.
All her damage and buffs scale off of her Max HP, so ATK is useless to her.
S-Energy and U-Energy are not useful to her as a support.
If using Freefin as a main dps, then U-Energy recovery is a decent cope stat.
Since Siris only deals skill damage, and skills can't crit, crit buffs are useless to Freefin.

Shield Construction Efficiency is a cope stat of you are using Freefin on-field, but if you are only using her as an off-field support that's useless too.

Whilst Freefins support skill does have a 5s cooldown, it only goes on cooldown after all Wavehunt stacks have expired, meaning that in practice the uptime is high and the time between casts is much higher than 5s. As such Twilight squad is not a good choice.

Manifestation

M1 gives her Support Skill 20 Wavehunt rather than the initial 5 stacks.
This gives max wavehunt up-front, and thus gives the maximum thermal damage buff immediately.
It also allows operatives who deal skill damage infrequently enough to be unable to maintain Freefin's support buffs a longer uptime on the buffs.
It also gives +5% Final Skill DMG when at 10 or more Wavehunt, which most skill damage operatives can maintain.
Even if an operative can't maintain it, since they now start with 20 stacks they'll get some decent uptime on it anway.
+5% Final DMG is decent, but not that strong, and it doesn't change how Freefin plays.
M2 gives any operative with Wavehunt ignore 10% All-Type Resistance and 5% Thermal Resistance.
This is good for all operatives, but obviously a stronger buff for thermal damage operatives.
M3 causes targets with a Wipeout mark to take 12% more skill damage.
Given how rare "damage taken" mods are, this is very strong
M4 gives the usual +1 skill level, as well as buffing the buff that Wavehunt gives, which is very nice.
M5 just gives +15% ATK when at 10 or more Wavehunt stacks.

If you want efficiency (good damage with minimal investment), then M3 is a good stopping point.

Good teammates for Siris - Freefin

Freefin works with any operative that deals skill damage.

Freefin works best with operatives who can maintain at least one wavehunt stack, however almost all skill-damage operatives can.

Freefin works better with operatives who deal thermal skill damage, but the difference is small, although it gets larger at M2.

Since Freefin ideally only deals damage when she first uses her support skill, and ideally only does that once per fight, that means she also works perfectly with Celestial Swan, even for operatives that don't deal thermal damage.

The best operatives to use Freefin with are

Siris - Ksana deals exclusively Thermal Skill Damage and can maintain max Wavehunt stacks, making her an ideal partner for Freefin.
Fenny - Pureheart deals almost entirely thermal skill damage, and hence works extremely well with Freefin.
Fritia - Hush spends most of her time in combat shooting stuff, but most of her damage is in her ult, which works well with Freefin as Hush' ult is entirely skill damage.
Nita - Pulse deals exclusively Thermal Skill Damage, and can use skills extremely frequently, making her a good pairing with Freefin, however since Pulse' damage scales with Max HP, Freefin's ATK buffs are wasted on Pulse. Freefin is still a very good support for Pulse, but their synergy isn't ideal.

Note that Siris' Ultimate isn't worth using with any current dps operative, as there is no scenario where you would want to swap out your main DPS to have Freefin swap in and start doing damage - you're always better off just maintaining Freefin's support skill and having it buff your main DPS.

Further note that Freefin's ultimate cost 60 U-Energy, which is more than Fenny - Purehearts ult uses and that Pureheart tends to generate via her standard LMB combo chain, which means that the only time you'd actually want to use Freefin's ult is when using Pureheart and are only using Purehearts RMB attack.

If having Freefin support Pureheart whilst Pureheart uses her LMB combo, you'd need to not use Pureheart's ult for a while to gather enough U-Energy to swap Freefin in via ult, which is a large loss of dps for Pureheart.
Siimilarly, Pureheart offers absolutely no support buffs to Freefin at all, so whilst Freefin is on the field Pureheart is basically just dead weight on your team.
If you are using Pureheart as your dps and using Purehearts LMB chain, then it's never worth it to ever swap Freefin in via her ult.

Since Pureheart's RMB attack doesn't allow Pureheart to use her ult, any U-Energy she gains is useless for herself, and thus allowing Freefin to use it for her ult does work, however since Freefin isn't really any better at AoE than Purehearts RMB attack is, you really wouldn't need or want to ever do this anyway, but you could.

As such, I recommend that if you are using Freefin as a support for another dps, then you should never use Freefin's ultimate ability.

Overall

Freefin is a fantastic skill damage support.

She provides skill damage buffs that work universally with all operative that deal skill damage and can work alongside Celestial Swan, however Freefin does work best with operatives that deal skill damage, and ideally thermal skill damage.
Despite that, she is a very strong skill-damage support.

Her ult isn't useful if you're using her as a support though, as using her ult forces her into a Sub-DPS or main-dps role, which she doesn't deal enough damage to ever be optimal at, whilst also offering no buffs or team-wide utility while she's on the field.