The infamous Gloom can be a difficult ability to apply if you can't balance your stats and maintain your Energy. Thankfully, [Trinity] possesses a couple of ways to restore Energy, and with the right mods and Focus School, we can make Gloom especially effective for her, and establish what is arguably the best crowd control Ability in the Helminth on one of the game's oldest reliable support frames. It's time to slow their roll, with Gloom Trinity.

Mod Breakdown:

-[Brief Respite]
Our usual Shieldgate mod, since your Efficiency is so low that even Well of Life could reset it if you have 4 Augur mods with it (which we can do with a Sentinel with Burst Laser OR the Secondary weapon, whichever one you want to place the two Augur mods on).

-[Blind Rage] (rank 9), Molt [Vigor] + Madurai Focus School
Naturally, you want high Strength for Gloom. By using Molt [Vigor] and the Madurai School, you [Reach] 275% Strength, which caps the Slow at 95%. Since nothing else in this build needs more Strength (Damage Reduction from her abilities needs only 150% Strength to max out), we only have [Blind Rage] at rank 9, which saves a touch of Efficiency while still reaching the cap for Slow (feel free to use a max Blind Rage if you don't have a rank 9 available, it won't hurt).

-Stretch, Cunning Drift, Augur Reach
With these, Gloom reaches just over 30m, Link hits 38m, and Well of Life's healing/status immunity Aura comes to 28.5m; with all these defensive measures in place, it's truly a skill issue if you end up dying.

-[Primed Continuity], [Augur Message]
With [Blind Rage] tanking your Efficiency, your Energy Drain from Gloom becomes a situation. With these, your Drain is recovered; your Drain is now at 84%, which is maximum 6.3 Energy/second if 10+ enemies are inside Gloom's radius. You'll also maintain Link and Blessing's Damage Reductions almost twice as long (which combined with Link's damage redirect and Gloom's ability to heal you when you damage enemies, you'll be rather tanky on this build for an extended period of time provided you keep 3 and 4 constantly active).

-[Pool Of Life], [Equilibrium]
I'm sure you noticed that I put Gloom over Energy Vampire. That was not a mistake. The reason for this is because EV can't recoup your Energy while Gloom is active. This means you'd have to deactivate Gloom, cast EV a time or two, and recast Gloom. It'd be a somewhat consistent interruption of otherwise fluid gameplay. So, we flip the situation -- Subsume over EV instead of Well of Life, and then turn Well of Life into the Energy maintenance skill using these Mods. When you cast Well, focus on the target with your weapon to deal significant damage; all the damage will be stored up until Well is expired/deactivated. You'll also be protected from status effects while in vicinity of the Well target, and each status effect negated damages the enemy 10% of its max HP. Once you're sure they'll die from the stored damage, deactivate the skill; with their death comes a small plethora of Health Orbs (especially if your pet got involved with their Synth mods in tow), as well as an Energy Orb with at least at 90% chance for a second one. One cast will return 245 Energy minimum. And best of all, Gloom is still active to slow down everything around you. Personal recommendation -- when the ability expires, go ahead and recast again to keep a steady supply of Orbs as well as maintaining Status immunity auras, and only deactivate manually if you're moving locations or need Energy sooner than later.

-[Primed Flow]
Because of your low Efficiency, casting anything will be twice as expensive as usual, not to mention Gloom's Drain can catch up with you if you're not paying attention. So you'll want the reserves to afford it all.

-Arcane Eruption
Eruption is to offer an additional layer of crowd control by giving a constant knockdown over a 30m radius each time you pick up an Energy Orb (and thanks to [Pool Of Life], you can spawn them at will). This knockdown synergizes well with Gloom, as enemies will take 20x longer to recover. You'll practically be shooting fish in a barrel.

-Archon Shards
You should easily get by with just one Amber Shard for Casting Speed, especially if it's Tauforged; you may not even need that since we're using Madurai to push Gloom to the max Slow, and it comes with Casting Speed as well, so feel free to set that off periodically if you wish. Either way, I would dedicate the rest of your slots to Ability Duration; the more Duration you have, the less Energy Gloom will drain, and the longer Well of Life, Link and Blessing will last.

-Alternative Options
Right now, the build is too tight to afford any changes outside of maybe swapping Arcane Eruption for a personal preference. Should things change in future updates, this will be modified to include potential ideas.