Greetings!
My name is Kushemon, and I would like to guide you through this [Protea] build.

This is a endgame build, optimal for usage in long Steel Path endurance runs.

Thanks to the fairly recent addition of Archon mods and shards, [Protea] has benefited immensely, and became even more prevalent in SP (Steel Path).

The essential parts of this build are the Archon Vitality, and of course, the beloved, Huras Kubrow with Stalk.
Since [Protea]'s Artillery doesn't interrupt the stealth granted by our Kubrow, she can put out immense damage, without standing in harms way.
I also suggest using the Zenurik Path, Molt Augmented and Molt Efficiency.
Although they improve on the build immensely, with their added 60% strength and 36% duration, they are not required.

Assuming you used both the Molt Augmented and the Zenurik Path on this build, you can easily create an infinite income of Energy and Health Orbs.
With a fully stacked Molt Augmented, which can be done fairly swiftly, and using the Hardened Wellspring, plus [Protea]'s passive, you can create a Dispenser with a 100% chance of double drops, returning your investement withing threee seconds.
With the additional passive Wellspring energy income, and Energy Orbs dropped from enemies, you will almost never run dry.
And you won't even need that expensive Arcane Energize!

Moving on to another one of our important additions, the [Archon Vitality].
Considering that [Protea]'s Artilery deals Heat damage and procs the Heat status effect, the instance I saw this mod, I knew it would be the perfect fit for our little engineer.
With this mod, you can instantly reduce the enemy armor to shreds (by 50%) using your turrents.
During our Artillery's life time, it can proc to about 40-80 Heat status effects on multiple enemies.
Heat also provides excellent crowd control, and on higher levels, when [Protea]'s single Artillery can't oneshot a full room on it's own, you can bet the Heat DOT will finish the job.

If all of this isn't enough, I also suggest using a Decaying Dragon Key.
Yes, yes. We all know it is overused and abused beyond limits, but if you really don't feel like dying today (in game ofc), it can be of great help.
[Protea]'s Grenade Fan can provide instant overshields to reset the shield gate, and don't even mention the additional three seconds of invincibility.
This is a great lifeline, may Warframe Kubrow A.I. decide; "I don't feel like protecting my owner today....".

Grenade Fan can also provide good protection to your Kubrow, shall it encounter unwanted AOE damage.
You can call your in your loyal friend by pressing X two times, in case of emergency.
Once your Kubrow dies, you will most likely too (without a shield-gate), so watch out.

But let's talk about weaknesses now, because few builds have none, and this isn't one of them.
Nullifiers. We all knew this was coming.
[Protea]'s biggest weakness, are Nullifier bubbles, especially since you can't deal with them with firepower or your melee, as that would break our stealth.
What I would suggest you do, shall you encounter one of these, is to place your Artillery in such a way it will be able to target enemies around, and behind the nullifier.
As the turrets deal AOE damage both around themselves and the enemy they shoot at, they can gradually chip away at the Bubble.
Usually just one stray enemy who dares step outside of the "blue safe sex dungeon" will be enough to destroy the bubble.
Your kubrow can also destroy the bubble pretty quickly with Bite, but this is very dependent on Crit and targeting RNG.
But don't worry about entering the bubbles, as it will not break the stealth granted by [Stalk]. You will however lose your active Grenade Fans.

You may have noticed this is a 2 forma build, but quite frankly, there is no need for that.
Just one forma is plenty, if you don't have all the mods ranked up to the max, and even then there is no need to do that.
However if you are a true "min-maxer", with the addition of a few formas, you can replace [Intensify] with its Umbral version, for even more destructive and supporting power.
You should then also be able to include an exilus mod. Choose whichever one feels the best for you, as it honestly doesn't matter.

Please let me know what you think about this build and the guide, as this is my first time doing one. Any questions or suggestions are also appreciated and will be answered.

Also yes, I am aware of GHS making a video with a very similar build ([Huras Kubrow] + [Protea]), but I believe I have made enough changes and improvements, for this build not to be considered plagiarism.
I hold nothing but respect for GHS!

A similar [Xaku] build, also utilizing [Huras Kubrow] is on the way, so stay tuned.
Until then, goodbye!