Note: This build is NOT specifically for Excalibur (Prime/Umbra), but rather a "universal" build fit to work on virtually any Warframe, provided the Duration, Range, and Strength don't hinder their other abilities.

The purpose of the build is to hit 3 benchmarks with Gloom:
1. Between minimal and neutral Drain.
2. Maximum Slow.
3. Radius no lower than 25m.

Also note that any empty slots above are considered "flex" for the sake of the build; only the bare minimum needed to complete the prior 3 benchmarks is listed.

Universal Gloom Version 2: Durable and Destructible

This version of "Universal Gloom" has fewer flex slots than the first, but at least triple the Duration since we forfeit Fleeting Expertise for Boreal's Hatred. And since our Efficiency is still fairly high at 145%, you should be fine without using Flow/[Primed Flow] unless you spam abilities (which if your Duration is higher, you're probably not doing that). This version is for those Warframes who need that extra time.

As with Version 1, there are a few additional requirements for this build to work:

-Madurai Focus School
With the bonus 40% from this school, we can snapshot our Ability Strength high enough to maximize Slow at 95%.

-Crimson Archon Shards
Any combination of Shards to [Reach] +30% or higher Ability Duration. If you push for +60% or higher, you could cut [Constitution], or you can remove Molt Efficiency if you push +65% or higher.
OR
If you use your Crimson Shards instead to [Reach] +45% or higher Ability Strength, you can cut [Transient Fortitude] out of the build. You still maintain maximum Slow, and this will add back 27.5% Ability Duration, which allows us to snapshot it at 219% (to have minimal Drain with 145% Efficiency, you need 220% Duration; you're literally on the brink that you can add another mod or Shard to cover it, or just go without if you wanted). Either of these options for Crimson Shards can add a flex slot back into your build, but this one theoretically could take fewer Shards to pull off.

What flex slots you have available to you can be used for things such as [Combat Discipline], [Brief Respite], [Growing Power], [Primed Sure Footed], Cunning or Power Drifts, augment mod(s), [Primed Flow], Arcane Energize, Arcane Avenger, etc.