NOTE: This is a fairly high-investment build and not the best CC bang for your buck, so unless you're really interested in going all-in on this specific concept, I don't recommend building for this. It's more performance art than utility knife!

NOTE #2: Tying in with the above warning, this build depends on archon shards and/or well-invested arcanes to really hit top gear. I use 2 Tauforged amber shards for energy regen on orb consumed - this isn't absolutely necessary but helps, especially if you run a low-density mission or don't have r5 Energize. I also run 3 crimson shards, which you really do want to use if you want to hit maximum Gloom slow or close to it. Molt Vigor (or Molt Augmented, up to taste) is pretty mandatory for the same reason.

Strategy

This is very simple, gameplay-wise. The entire build revolves around Gloom extending Miasma's stun animation, which causes enemies to flail around, weaponless, for the duration of said animation. You can probably guess where this is going.

The approach is thus: pop your Drifterator ability of choice (to proc Molt [Vigor]); attack an enemy to proc [Growing Power]; activate Gloom and swing away (or, if you prefer, make a cup of tea while you watch Spores tear your enemies apart). Press Miasma every 25 or so seconds and watch the entire map become completely immobile for the next 25, barring Overguarded units. Great fun for things like interception because the stun animation produced by Miasma stops enemies from hacking the consoles. I regularly use this build to solo SP interceptions.

Stats breakdown

High range is pretty self-explanatory if you want to immobilize the whole map with a range-scaling skill like Gloom or Miasma. High strength is also clearly important for the sake of Gloom's slowing effect, and high efficiency helps with Gloom's drain (especially in high-density missions where lots of enemies will push the Gloom energy drain to its max cap). Duration isn't too important because Miasma's stun animation is not tied to ability duration (only the time enemies spend taking viral damage from it) and because Toxic Lash scales such that it actually has pretty high duration even with ability duration under 100%. The negative duration also won't hurt your Spores too much, though this is not really a Spores-centric build (since I often use this in higher levels, like level cap endurance, I stick with weapon damage for the most part; Spores are an [Enemy Radar] bonus for me at that point).

No real survivability mods here (other than [Handspring]) because this build very much empowers you to survive even as a glass cannon; plus, optimizing for the gameplay concept here has you spending lots of slots on strength, efficiency, and range already, leaving little room for eHP as is. I like Handspring because it strikes a perfect balance between being a cheap mod (no waiting till login day 400 if you haven't yet! No 16-capacity drain!), letting you survive easily (with [Handspring], my knockdown recovery time is quick enough that I can use a Vazarin dash and [Recover] my shields even at level cap), and leaving you feeling like there's still a tiny bit of engagement in your gameplay (okay, this one is really up to taste). Feel free to use Primed Sure Footed or the alternative exilus of your choice, however - anything goes!

Let's talk arcanes. I picked Arcane Energize because, again, this can get to be a little energy-heavy between constant Gloom uptime and Miasma spam. If you don't have Energize, you have plenty of other options - from those amber shards I mentioned (I use both purely for comfort; lets me ignore the energy drain debuff in high-level disruption, among other things) to Emergence Dissipate (also an arcane, but goes on your Drifterator instead) to even [Equilibrium] (which is now stronger than ever, and which you could probably sub in for Primed Flow, if you feel like you aren't spamming enough to really drain that ginormous energy pool of hers - your playstyle may vary; I'm very spammy). Worth noting also that I use [Seismic Bond] on my pet (a trusty [Panzer Vulpaphyla]), which further increases my efficiency (29% at max stacks). Molt [Vigor], on the other hand, is crucial for boosting strength so you can get Gloom as close to max slow as possible. Why do I use [Vigor] instead of Augmented? Basically because sometimes I like to run this build in fast missions where I don't expect to kill enemies at a rate such that Augmented will ramp up quickly (think one or two rounds of interception, for example). However, Augmented will absolutely give you more strength and is the pick of choice if you run this in endurance or any kind of longer mission, and I do have a variant config with that in place instead.

Other stuff: I use Vazarin as my Focus school here because I am a filthy Vazarin main and also because it's the perfect shieldgate complement in higher levels (notice that I have no innate way of regenerating shields on this build and even if I did, my efficiency is so high that I would have to spend a lot of mods to effectively do so via ability cast). However, feel free to use the school of your choice! You could probably squeeze out space for [Rolling Guard], for example (I'd vote to sub it in for [Augur Secrets] or [Primed Flow]), so you don't need Vazarin's Protective Dash to give you that breathing room for shieldgate purposes. Or you could choose not to shieldgate at all, especially in lower levels, where the lifesteal from Gloom will become relevant. The Miasma stun time gives you a lot of elbow room - just make sure you aren't getting ganked by an Overguarded enemy in the meantime.

For Archon Shards, I use 1x Tauforged Crimson (to really beef up that Gloom slow), 2x Tauforged Amber (because I like feeling very secure about energy - but this is overkill, really), and 2x regular Emerald (this lets me full strip with just Spore casts). Alternatively, use more Crimsons for extra Gloom strength.

Where can (or should) I use this build?

I've used this to good effect in solo play everywhere from short interceptions to endurance survivals, level cap disruptions, and more. The short of it is, wherever you like! Except...maybe not defense. Especially if you have any teammates. They will probably suddenly all remember they've left the stove on and leave in a hurry if you use this build there.

You're insane.

All the best people are! ;)