This build essentially doesn't care about using abilities and is intended to survive whatever gets thrown at it, letting your guns do all the work. The ideal use case is high damaging bosses (Eidolons & Orbs) and Steel Path enemies.

For this build to be any kind of useful, you need to have good weapons, or you probably won't do anything useful other than survive to revive teamates.

MODS

[Stand United], [Umbral Vitality], [Umbral Fiber], [Gladiator Resolve], [Gladiator Aegis], [Adaptation], and [Carnis Carapace] are the core mods of this loadout, there's nothing else you'd really want more than them. If you don't have the Gladiator or Carnis mods, you can always sub in some of the alternates below as well.

You can technically replaced [Stand United] with Rejuvenation if you have no other source of healing, but there are plenty of ways to heal from health orbs, healing deployables/gear, allied warframes with healing abilities, Vazarin Focus, Arcane Grace, Magus Elevate, Magus Nourish, Magus Repair, and Voracious Metastasis, that you shouldn't really need it.

[Primed Sure Footed] is to avoid bad situations as well as just make life less annoying, and can be exchanged for [Coaction Drift] for more armor.
[Rolling Guard] is mainly used for status cleansing, and can be exchanged for [Health Conversion] or [Armored Agility] for more armor.

[Umbral Intensify] is highly recommended for the benefits it grants to [Umbral Vitality] and [Umbral Fiber], but upgrading it is unecessary (however, it is useful for Warcry and your Subsumed Ability). If you already have it upgraded, another Umbra forma will be needed, or up to 3 more regular forma if you put on all the most expensive variations (those being Armored Agility, Health Conversion, Primed Sure Footed, and Rolling Guard).

ARCANES

Arcane Grace and Arcane [Guardian] are obvious choices for Arcanes, however you may wish to consider weapon damage options instead, since that will be your only way of dealing with enemies. I personally use Arcane Precision and Arcane Awakening to buff my secondary weapon, though there are options for primary or melee weapons as well.

Magus Elevate, Magus Nourish, and Magus Repair are all also fantastic choices to give yourself a quick heal if you dont use Vazarin Focus and want some quick on demand healing via operator mode.

FOCUS

Recommended Focus to go with is Vazarin for an on command heal/invulnerability and instant revives for you and your whole team, if you want to dedicate fully to the role. It also increases your teams affinity range, which scales with Voracious Metastasis, details later.

A more support oriented playstyle is recommended with this build unless you are doing Eidolons, in which case go for Madurai for amp and weapon damage, or Unairu for the wisps and armor as a bonus.

Unairu is an good option if you really want the extra armor, and while the wisps can be helpful, Vazarin is much more valuable to the team.
Similarly, Zenurik is okay in order to give your teamates energy, but doesn't really do anything else useful (as energy isn't nearly as important to this build).

ABILITIES

While you won't be using abilities much, they're still useful at base level:

• Ripline is cheap mobility to move around faster or to save a failed bullet jump.
• Warcry is a solid armor buff, as well as slowing nearby enemies. If Umbral Intensify is upgraded, it can be very potent even with the short range and duration.
• Paralysis is an extremely cheap way to open enemies up to finishers. If you are close enough to them, you can get two finishers off per paralysis.
• Hysteria is nearly useless on this build, you're already essentially invulnerable, and they cost too much energy to sustain them if you want to use them for damage. Rolling Guard makes a better panic button if you really need it for that reason.
• Infested Mobility is decent mobility option that's fairly cheap to unlock, but isn't at all necessary, and should be replaced with Voracious Metastasis (it's not on the website yet).
• Voracious Metastasis is an insane tool for this build, and is highly recommended to use it once you unlock it, details below.
• Other options are literally any defensive or mobility ability, preferred if they don't scale with Range or Duration, or have a low energy cost. Scaling with Strength is a bonus if you upgrade Umbral Intensify.

VORACIOUS METASTASIS

Voracious Metastasis gives you 500 health over 10 seconds, more with higher Strength, but slower with higher Duration. Our base Duration means we don't have to deal with slower healing compared to an [Eternal War] build.

Additionally, Voracious Metastasis gives 50 energy to all allies in Affinity Range, not affected by Range, but it is affected by Efficiency, meaning that our base efficiency comes in handy by giving more energy per second to allies than if we had high Efficiency.
It should be noted that the affinity range used by this ability is affected by Vazarin's Mending Unity, just like [Harrow]'s Covenant.

Overall, the mix of scaling negatively with Duration and Efficiency, and having what is essentially a strong regeneration effect and grants allies energy, just makes this the perfect ability for the build.

SUMMARY

I'm going to be honest, this build is an extremely simple premise, simple playstyle, and is basically just a brute force method to endgame content. You won't be getting any speedkills on Eidolons or Orbs, your stats won't be outstanding in any way, and you might struggle with defense objectives. It's fairly expensive to bring it to realization, even if there are plenty of cheaper substitutes, and due to the forma polarities it can lock out other builds in your other loadouts.

But that's not the point. The point is, you will never die. You can sit there and take barrages from the most highly damaging enemies in the game without sweating. You can do the [Endurance Drift] challenge just by sitting there. Steel Path will become much more manageable if you have the guns for it (barring defense missions).

If you want 99%+ damage reduction with no upkeep beyond [Adaptation], this is the way to do it.