Mauxir - Lotus

If you don't have Mauxir - Lotus yet but want to try her out, then whilst she is not available as a Trial Operative in any Story Mission, previous Auctus Drive operatives have been added to the main story shortly after they have been introduced, so Lotus likely will be as well, replacing Mauxir - Shadow Ka as the Trial operative in Story Chapter SP8 "Reflection of Valor"

As an Auctus Drive character, Lotus is being given away for free during her initial release, along with all her Auctus Drives, her 5* weapon at T2, and a fixed-stat logistics squad.

Lotus creates a bunch of Auxiliary units who deal damage for her, with Lotus mostly just shooting her drones to restore their HP and recharge her ult - If played properly Lotus deals literally no damage by herself, and is entirely dependent on her summoned units for damage.

Her summons being immobile means you need to re-summon them for every new group of enemies, meaning Lotus can potentially feel very slow to play in casual content.
Needing some time before Lotus reaches her drone cap means she can be somewhat slow to start dealing damage too.
Her summoned units being both immobile and killable means that Lotus can struggle to maintain her dps against some high-dps enemies who can kill her summons.
Lotus herself can potentially have extremely high survivability though.

The Basics

Role: Main DPS and Damage-Support
Deals Frost Damage
Weapon Type: Sniper Rifle
Her Drones deal damage for her.
Lotus ideally doesn't deal damage.
(but purely ballistic if she does)
Mobility is Average

How to use Mauxir - Lotus

If Lotus doesn't have 3 Nodes active:
Tap Lotus' Standard Skill to create 1 Node.
These will automatically create drones.
Both Nodes and Drones are immobile, and attack automatically.
Every 10s, hold her Standard Skill to grapple to and enhance a Node
(The petals on the Nodes icon shows its remaining duration)
Otherwise, shoot your Nodes with Lotus' sniper rifle.
(This also heals them, so shoot the one with the lowest HP)

Notes:

Lotus shooting her Nodes will spawn a drone, thus reducing the cooldown of her ult via her Auctus Drive A2 effect.
Lotus' ult buffs her Nodes/Drones damage by an extreme amount, and Lotus' gun deals basically no damage, so it's better for Lotus to use her gun to shoot her own Nodes to recharge her ult than shoot the enemy.
Again - Do not ever shoot the enemy.
Nodes have a blue PBAoE around them. Stay outside of that area.
(Lotus' grapple [Step.2 in the above] doesn't work if you're too close)

How to build Mauxir - Lotus

Weapon: Enlightener
Weapon Parts: Max ATK
Logistics Squad: Totem
+10.0% ATK
+106 Alignment Index
+10.6% Auxiliary Units Strength
Best supports:
Vidya - Celestial Swan (or Acacia - Kaguya if not)
Tess - Phantasia (only with her Arcane logistics)
Note: Tess' support skill is useless for Lotus
Tess is only useful because of her ult w/ Arcane

Specifics:

Standard Skill

Tap Lotus' Standard Skill to deploy a "Mindflower Node", which is an auxiliary unit that attacks the nearest enemy every 2s, dealing AoE Frost damage.
This AoE Frost damage hits the targeted enemy and up to 2 additional targets, for 3 targets total.
Lotua can have a max of 3 Nodes at a time.
Creating a new Node when at the max will create a new Node whilst destroying the oldest Node.

Each Node has a 50% chance to deploy 1 "Lotus Drone" each time it attacks. Each Node can have a max of 5 drones, or 10 with its first Neuronic.
Nodes deals Frost damage to the nearest enemy every 3s.

Lotus has a unique HUD icon to show where each of her Nodes are.

The Nodes have unlimited duration, but can take damage and be destroyed.
Each Drone lasts 20s, and are untargetable and cannot be damaged/destroyed, but if a Node is destroyed then all of its associated Drones are destroyed with it.

Nodes and Drones aren't destroyed when Mauxir leaves the field, but they become dormant and stop attacking.
Nodes can still be damaged in this dormant state.

If Mauxir shoots at or through a node then it is healed for 15% of its Max HP.
With its second Neuronic buff, shooting a node to heal it will deploy 1 Lotus Drone.
This will proc Lotus' A2 bonus, reducing the cd of her ult by 1s.

Note that both Nodes and Drones are completely immobile.
Further note that Nodes will block your movement.
If you accidentally block your path, you will have to resummon your Nodes, as when at the Node cap, summoning a new Node will destroy the oldest Node.
Also: Yes, you can use this in multiplayer to block the path of your allies.
Since the Nodes last forever, there's nothing your allies can do about this.

When Mauxir has a Node active, you can hold her Standard Skill to grapple Mauxir towards it, which also enhances the Node and all of its Drones for 10s.
Enhanced Nodes and Drones deal double damage.
Only the most recently pulled node can be enhanced - if you enhance a new Node, the old Node loses its enhancement.

Mauxir can only grapple to and enhance a Node if she is outside the Nodes blue PBAoE area.

This skill has a 0.5s cooldown and an S-Energy cost of 5, meaning you can create the max of 3 Nodes extremely quickly, and Lotus should never have any S-Energy issues.

Support Skill

Mauxir deploys 10 "Clusterbud Drones" in front of her (15 drones with its first Neuronic), which deal Frost damage to the nearest enemy every 3s.
Each drone lasts 20s.
Since this skill has a 20s duration, you can get essentially 100% uptime on it by just spamming it off-cooldown.

Since this skill has a 20s cooldown and uses 20 S-Energy, Mauxir recovers as much S-Energy as she uses, so she doesn't run into any S-Energy issues.

Each of the 15 drones deals damage every 3s, and fire a total of 6 times over their duration.
Since each drone deals 24% of Mauxir's ATK, this means that over their full 20s duration they deal a a total 2,160% damage combined.

This is extremely high for the support skill of a main-dps operative, and it makes Mauxir an ok support operative, although you're generally still better off using another support to buff your main dps, rather than using Lotus to deal damage herself.

Ultimate Skill

Mauxir performs a "Dance of Life" which enhances her Nodes and Drones.

After the Dance ends (which takes around 4 seconds), her Nodes/Drones are further enhanced with 100% Attack Speed Boost until the dance ends - which takes 10s.
The cooldown for her ult starts after this 10s Attack Speed Boost ends.

Mauxir is immobile while she dances, but with her Neuronics she takes less damage and receives CC-resistance to help prevent her from being interrupted.

This has a U-Energy cost of 0, so Mauxir can always use it, even immediately as a battle starts (not that you'd want to, as you're better off using it after some Drones have spawned so that they can make use of the buffs).
This skill has a 70s cooldown, and it goes on cooldown only after it has ended, so it's something you will often only be able to use once per fight.
Her Auctus Drive A2 buf can help with this, but even with max investment you'll be able to use her ult every 40s or so
A 10s buff on a 40s cd gives around 25% uptime.
Given that it doubles her Node/Drone damage, and then doubles their attack speed to double it again, it's a 4x damage bonus.
A 4x damage bonus on a 25% cooldown means Lotus' ult will on-average very roughly result in +75% damage as a result of her ult.
This ignores her logistics squad, which buffs her ult even more.
Even facotring in it's long cooldown, Lotus' ult is extremely strong.

Weapon

Enlightener
Lotus' signature 5*, and her best weapon.
More Auxiliary Unit DMG, and helps deploy more Lotus Drones.
Targets taking 0.5/0.7% more Frost DMG per deployed Lotus Drone is a max of 15/21% more Frost DMG Taken, which is very strong.
Note that this gives Alignment Index instead of the more common ATK Boost that weapons normally have, giving up to +549 Alignment Index at max.

As usual for signature 5* weapons, the "enemies take more DMG" part of her 5* is its strongest aspect, but Enlightener increasing Aux Unit Strength as well is also very strong, as that's not something found on other sniper rifles, making Enlightener even better in comparison to other snipers.

Like all Auctus Drive operatives, Lotus has no signature 4* weapon.
As such, if you don't have her signature 5* weapon, then you'll want to give Lotus the highest-levelled Semi-Auto sniper you have lying around - since most of Mauxir's damage comes from her Nodes/Drones which are Aux Units, none of the weapon effects from other weapons make much of a difference to her damage, so again - just use whatever you have lying around.
Make sure it's Semi-Auto though - Mauxir's ability to shoot her own drones to heal them mean Lotus can potentially benefit from a higher fire rate beyond just having more damage, and a lower-levelled Semi-Auto Sniper can out-dps a higher-levelled Bolt-Action sniper if Mauxir can keep her Nodes alive longer with the Semi-Auto.

For weapon parts Lotus wants maximum ATK.

Logistics

Use Totem squad - it was designed specifically for her and is her best choice.
Totem squad gives Lotus +40% Auxiliary Units DMG, which is a very nice buff, and an extra +45% during her ult's Dance, which is also really nice.

If you don't have Totem squad, use

Usha squad for the extra Aux Unit buffs - just make sure Mauxir keeps shooting enemies - at least one shot every 3s.
Twilight squad - Lotus' Aux units will constantly proc the effect for a permanent -16% Frost damage resistance.

Lotus can't make use of Twilight's 2/3 bonus, but can make use of Usha's, so Usha does work out well.

For Stats, Mauxir wants:
Basic: +10.0% ATK
+106 Alignment Index
Special: +10.6% Auxiliary Units Strength

Her Nodes and Drones inherit her ATK, so Mauxir wants maximum ATK.
Aux Unit Strength buffs the damage of her Nodes/Drones.

Alignment Index gives Mauxir more Auxiliary Unit Strength.
A max-roll of +106 Alignment Index gives +8.48% Auxiliary Unit Strength.

Mauxir's Support Skill has a 20s duration and a 20s cooldown, so she doesn't need S-Energy Regen or Skill Haste
Her Standard Skill has a 0.5s cooldown, so she doesn't need Skill Haste for that either, and since Mauxir should ideally only need to summon 3 Nodes per fight, S-Energy Regen isn't useful either.
Her ult has a U-Energy cost of 0, so U-Energy Regen isn't useful for her either.
Mauxir can't heal or create shields, so Heal Bonus and Shield Construction Efficiency are also useless for her.

Since Mauxir herself deals basically no damage, stats like Crit Rate, Crit DMG Amplifier are basically worthless for her.

Auctus Drive [i.e. her Manifestation]

With A1, whenever Lotus creates a Node, it automatically creates a Drone.
In an ideal fight, this doesn't affect her sustained dps by much.
If her Nodes are being destroyed a lot, then you should probably use another operative, but if you did use Lotus A1 would be a good dps increase.
Overall, A1 is not a massive dps increase.
A2 reduces the cooldown of her ult by 1s for each Lotus Drone deployed.
This can result in a lot of cooldown reduction, and A2 improves the uptime of her ult dramatically.
A2 is a extremely massive damage buff for Lotus.
A3 gives a +20% Final DMG buff to all Nodes and their Drones whilst they are enhanced.
Combined with the uptime buff for her ult from A2, A3 is actually a good damage buff on-average.
With A4, when Mauxir is doing her ult Dance, all Nodes recover 10% of their Max HP every second.
This is a nice survivability buff, but obviously doesn't increase their dps unless it actually prevents them from dying.

As an Auctus Drive operative, you'll either have all of her Auctus Drives, or none of them.

Good Supports for Mauxir - Lotus

Critical Note: All of Mauxir's damage comes from her summoned Aux Units.

This section is much longer than usual, because Aux Units are weird...

Essentially all of Lotus' damage comes from her summoned Nodes and Drones, which are Aux Units.
As such, a lot of the common supports are mostly useless for Lotus, as their buffs don't affect Aux Units.

Lotus wants ATK buffs, debuffs to the enemies DEF and resistance, and nothing else.

Note that Lotus has a low ATK stat - her base ATK is low, her 5* weapon doesn't give her any ATK, and her logistics 2/3 and 3/3 bonuses don't give her any ATK.
Most dps operatives end up with 5-6k ATK when fully maxed. Lotus should have 3158.
Her low ATK stat means that flat ATK buffs are much more powerful for Lotus than they are for other dps operatives.

Aux Units and Double-Dipping

It is very important to note that when an Aux unit is crated, it's ATK is the same as the operative who created it, at the time of its creation.
If an operatives ATK stat changes after the Aux Unit is created, that will not affect the Aux Units ATK stat - the only thing that matters is the ATK stat of the summoning operative at the time the Aux Unit is created.
This means that you need to make sure her ATK buffs are applied to Lotus when she summons her Nodes.

This also means that some effects can be double-dipped, as you can use them to buff Lotus herself, who the Nodes inherit their ATK from, and the Nodes can then gain the ATK buff as well, allowing them to gain the ATK buff twice.
If these are percentage buffs, they will stack multiplicatively with each other.

Since Mauxir's Nodes have no time limit and last forever, you may only need to apply your buffs to Lotus once per fight, regardless of how long the fight lasts, provided you can keep her Nodes alive.

If Lotus can't double-dip, then that means the buffs apply to Lotus herself but not to the drones, which means that once you've created the Nodes there's no reason to ever apply the buff again.

Aux Units do not benefit from Skill Damage buffs, such as from Marian - Riptide's M2 buff or Siris - Freefin's Freetide buff.
Aux Units:
are not "full squad"
are not a "deployed operative"
are an "ally operative"

Best Supports

Vidya - Celestial Swan works by debuffing enemies, and she works just as well for Lotus as she does for all other operatives, and is Lotus' best support.
Acacia - Kaguya also debuffs enemies, and is a great support for Lotus if Celestial Swan isn't available.

Beyond debuffing enemies, how good a support operative is for Lotus is basically just a measure of how much of an ATK buff they can apply to Lotus, and whether it also applies to the Nodes and Drones as well and with what uptime.

Since Lotus' Auctus Drives aren't out yet, I can't test exactly who are Lotus' best supports, but for now, Yao is by-far the best only when double-dipping her ult.
Other than Yao's double-ult, Celestial Swan is Lotus' best support, but Celestial Swan only barely outperforms Phantasia.

For now, when tested individually, Lotus' best supports are (in descending order):
235% Yao - Nightglow when double-dipping her ult
188% Vidya - Celestial Swan when on her own - she'll perform better when she and Lotus are paired with another strong support.
182% Tess - Phantasia
164% Yao - Nightglow when not using her ult a second time.
145% Eatchel - The Cub
135% Siris - Freefin
This is just what I have tested so far. Again, numbers will change once I can test with her Auctus Drives.
Note that my Yao isn't maxed, and is giving less ATK than she could, so her numbers could be higher. That doesn't actually affect her position in the list though.
(I.e. even with max investment, Yao won't outperform Tess, although she'll get much closer.)
Regardless, Celestial Swan and Phantasia are Lotus' best supports, and that should be true regardless of the level of investment you have for Lotus or your supports.

Note that when supporting Lotus, the 4* support weapons outperform the signature weapons of all the operatives in the list above except Eatchel and Celestial Swan.
The 4* support weapons are Prismatic Igniter, Strawberry Shortcake, Deep Sea's Call, etc.
Eatchel's best weapon is still her signature 5* (Blitzing Fangs).
The extra Support Skill uptime from Celestial Swan's signature weapons mean they are still her best weapons.

Support operatives that do actually work with Lotus:

Tess - Phantasia

Phantasia's Arcane logistics squad gives a +35% ATK buff to operatives within the Realm of Wonder created by her ult.
Lotus can double-dip on this - use Tess' ult to apply the buff to Lotus, then have Lotus create her Nodes - the Nodes will inherit Lotus' buffed ATK stat, and Tess will then buff the already-buffed Nodes.
Since Tess' bonus is a 35% increase, the Nodes will end up with (+35% * +35%) = +82.25% ATK buff, which is extremely strong.

Since Tess' ult can have an unlimited duration and can be moved to stay on top of all the Nodes/Drones, maintaining that ATK buff for the Nodes is trivial.

Note that the aptitude buff from Tess' support skill isn't useful to Lotus - she should be shooting her nodes anyway, not the enemy, so since Tess' support skill doesn't give Lotus an ATK buff, it's useless to her.
As such, you don't ever need to actually use Phantasia's support skill.
If you have Tess' M2 bonus, you can use Tess' support skill and shoot the enemy every 5s to inflict the DMG taken debuff.

Tess is also on-element to Lotus, meaning she can be used with Celestial Swan, but since Tess doesn't generally deal damage when supporting Lotus beong on-element doesn't actually matter.

Yao - Nightglow

Yao provides a flat ATK buff (of up to +1,500 ATK) to all operatives within the Shimmering Stardome created by her ult.
Yao's Zephyr logistics squad also gives a +30% ATK buff during her ult as well.

You can get this buff almost immediately by just shooting with Lotus' sniper a few times, using Yao's ult, and then summoning three Nodes during Yao's Stardome.
Yao's ult might only last like 3 seconds, but that's all Lotus needs.
Lotus will get the ATK buff from the Stardome, which the Nodes can inherit.
The Nodes will retain their ATK stat even after Yao's ult ends, so Yao's ult having a short duration doesn't matter.
This is a very quick and very easy damage buff, and is quite strong.

If you aren't using Celestial Swan, you can use Yao's ult later when you have the U-Energy to do so, in order to have Yao's Stardome apply even more ATK to the nodes, as Lotus' Nodes can double-dip on Yao's buffs.
Nightglow conflicts with Celestial Swan, so you don't want to use her ult again later if using Celestial Swan.
If using Phantasia instead of Celestial Swan, you can spam Nightglow's ult.

Even if using Nightglow alongside Celestial Swan such that you don't want to use Yao's ult again later, the damage buff Yao can provide to Lotus is still very strong.

Eatchel - The Cub

Eatchel's usual ATK buff is strong, and provides the drones with a good ATK buff.

Eatchel can also heal Lotus' Nodes, although since Lotus' optimal playstyle is to shoot her own Nodes to heal them and reduce the cooldown on her ult, Eatchel's healing isn't overly useful as Lotus heals her Nodes for much more than Eatchel does, but the extra healing Eatchel provides is still nice.

Siris - Freefin

Freefin provides a +15% ATK buff, as well as a flat ATK buff equal to 1% of Siris' Max HP (so proably around +500-600 ATK depending on your investment).
Lotus can't double-dip on this buff, but it's still a decent damage bonus.
Since Lotus can't double-dip, Freefin doesn't need to do anything after providing her damage buff.

Siris is not an overly strong support for Lotus when compared to the above, but her damage bonus is still good.

Vidya - Agave

Agave's support skill provides a 20% ATK buff, which Agave can supplement using Prismatic Igniter to turn her into an actually quite good support for Lotus.
She's still a cope support and performs worse than all of the above, but Agave is one of the very few operatives who provides an ATK buff with no strings attached, meaning she is one of the very few operatives who can actually buff Lotus without relying on a 4* support weapon, logistics squad, or otherwise changing her default loadout in any way.
(Although if you want to use Agave as a support you should change her weapon and logistics squad...)

Any operative with a support weapon

The 4* support weapons (Prismatic Igniter, Strawberry Shortcake, Deep Sea's Call, etc.) all provide a 15s ATK buff to the deployed operative after their equipping operative uses their support skill.
Operatives using these weapons work well with Lotus, as their ATK buff can end up being quite large due to Lotus' low ATK stat.