There is a weird Lull build I tried for him paired with Savage Silence. Not super efficient but a fun change up of play style.

You want to get rid of his DPS ult for Silence? Interesting choice. How does that benefit / interact with your build?

~~Would've replied to this far earlier, but apparently Lemmy doesn't properly work on mobile browsers. Cool.~~

Isn't....that the exact opposite of what you'd want to do? Tharros Strike pairs exceptionally well WITH Coil Horizon, not in its place. CH is her grouping ability. Tharros strike is a strip in a small contained area. Dunno why people are so insistent on replacing her 2 when her 1's right there. It's never been particularly good.

Here's the build I use the most - archon shards are: 1x blue (tauforged energy) 2x yellow (cast speed), 2x red (duration, one tauforged). You likely won't need that many forma, I just had to swap polarities sometime ago so that's why there's 6.

Helminth is optional but if you use base build and use her 1 to hover Archon Stretch will be useless.

Helminth in this build is Spectrorage. Archon Stretch procs via tornadoes if you use an electric weapon (viral+electric). Phantasma Prime is my pick for that usually but you can use Amprex or whatever other weapon that works with that build. You can also use Gas weapons (for example, Gas Nataruk) and use normal Stretch. However the problem with Gas is that there's a nasty bug that will force you to recast 4 every so often as the tornadoes will disappear due to damage being capped at 500k (which is fed into by the gas clouds). Energize is flexible, you can use something like Arcane Arachne or some other damage boosting arcane. Not that more damage is required on her.

You can also put Spectro over her 2, replace Archon Stretch for normal and discard Funnel Clouds and feed your 1's hover via Energize.

Playstyle: keep up 3 at all times, use Rolling Guard when it expires or to protect from eximus abilities/Thrax Legatus BS stuff. Pick a nice spot, cast Spectro, hold cast 4 inside Spectro circle, use 2 to pull enemies into tornadoes (the tornadoes with augment will not pull enemies in by default but her 2 offers a bigger pull/ragdoll range anyway and will pull enemies into the tornadoes as if it was regular case). Aimglide to activate passive if you desire. Fire weapon into tornadoes. Watch everything die. Her 3 will protect objectives too and with big range you will not be affected by any ranged attacks, even aoe stuff. You just need to make sure you do not get melee'd.

Alternative Helminth skills, I haven't tested them all yet but I've seen those on different builds:

-Dispensary - with Equilibrium in place of Constitution and it'll let you drop Energize

-Silence

-Fire Blast - you'll need to swap Cunning Drift for Power Drift and swap Enemy Radar for Corrosive Projection so you can strip in two casts

-Nourish - for use with Gas bows to get Viral procs in cases of not being able to have the Panzer Vulpaphyla, energy multiplier is 1.4x at 40% STR but I swap Energize for Molt Augmented in there for full multiplier. Also great in Circuit with the energy generation on full HP decree.

-Spellbind + Spellbound Harvest augment (Molt Augmented in place of Energize) - status immunity on hold and energy recovery on regular cast

Dunno if it's the best build but it's the one that works best for me.

Zephyr really, really loves Aerodynamic and the Boreal mods.

Not OP but I also used Grendel extensively pre-rework. I think his rework was a massive improvement overall, but he's a different frame now, and not one that stands out to me as much. Being able to suck up an entire room pre-rework just felt great. The new version is an excellent frame that I use a lot, but I feel like the original fantasy isn't all there.

(The rework was totally necessary though. Before it, he only functioned with helminth abilities, which should never be true of any frame.)

I replaced Blood Altar with Breach Surge, they synergize really well. I use a heavy attack build with Life Strike on my claws to heal so Blood Altar isnt needed. [Blood Rush, Pressure Point, Killing Blow, Amalgam Organ Shatter, True Steel, Corrupt Charge, Life Strike + one elemental mod] One heavy slam near an enemy fills my health. If you arnt feeling super confidant with the healing claws as your only source of healing, id suggest subsuming Dread Mirror until you can wean yourself off Blood Altar.
Im not sure how Exalted weapon builds are selected for Circuit, and since ive gotten shafted with the wrong Dex Pixia build with Titania, I just slap the same build in every slot now.

So the build Im running is mostly strength and range [Transient Fortitude, Continuity, Auger Secrets, Intensify, Stretch, Power Drift] but the real key to the build is Adaptation, Quick Thinking and Primed Flow.
With Quick Thinking and Primed Flow your energy pool is now your health pool. Prioritize keeping energy full over your health with Bloodletting, its actually worth more effective health as energy than actual health. Adaptation helps you squeeze even more effective health out of your energy, in SP Circuit your shields are just going to be down pretty much all the time so you will likely need this.

For the Aura, you could do the basic bitch Corrosive Projection, or if you want to coke out those heavy attack claws a little more you could run Swift Momentum for that sweet +30% heavy attack wind up speed. Spam heavy attacks and basically be unkillable, Eximus seethe, Thrax boys melt, health goes up.
If you arnt running the coke claws but still dont want to run Corrosive Projection, try out Brief Respite and get 150% energy spent back as shields.

Basic rotation for dealing with a stack of enemies is: Seeking Talons -> Breach Surge -> Bloodletting while enemies are CCed by Breach Surge -> heavy attack or heavy slam at least once for health -> heavy attack spam or use weapons if you got something decent until your talons wear off -> repeat.

I just got back on WF after about a year of quitting. What's condemn build?

She needs armor strip (Terrify over her 2) so badly that unfortunately your gameplan tends to revolve around "kill everything before it gets a chance to hurt you". Fortunately due to just how busted Maim is with armor strip (as Maim scales off of enemy health and Slash damage, which Maim's burst deals, gets cucked by grineer armor pretty badly) that isn't too much of an issue....up to a certain point, where shieldgating (with a decaying key, unfortunately) becomes the only real option. Luckily unless you're playing Endurance runs you don't really need to do that, though. Even in SP she does just fine until... probably around the third C rotation or so, afterwards you'll want to swap to a slightly different shieldgating setup. Attached below is an example of two builds I use. The first one is my daily driver no muss no fuss it gets things done setup for when I don't want to actively pay attention too much. Second is the shieldgating setup, note the slightly lower efficiency on it. This allows 1 cast of Terrify to completely refill your shields and re-enable your full shieldgate, rolling guard's just there for added survivability. Again, though, the shield-gate build NEEDS a decaying key to work properly, she just has too much base shields otherwise and thus this build...doesn't -quite- work in SP Circuit, but you can make due by falling back to the typical strategy of 'nuke it with Maim before it nukes you'. 2 casting speed shards, 1 tauforged parkour shards, and 2 strength shards (for the first build, mainly) mostly just for taste and QOL. Molt Augmented's a requirement for the shieldgating build, less so for the 1st and you can just slot in whatever there.

You do not transition into Night Form at all with either build, but you still keep the 1 due to an annoying host migration bug that will oftentimes force you to swap into Night form regardless of whatever form you were in at the beginning of the mission due to your colors. If I had to guess, it's a weird coding thing with how Equinox's "default" state is code-wise. The amount of times I've seen Night form, or part of Night form, pop up randomly in mission end screens/host migrations/MR 30 bless statues confirms in my eyes that Night's just... the default/"first" in the code, if that makes sense.