Helloo,

being an absolute fan or Sevagoths Gloom, spiders and toxin damage, I came up with this build, cranking up the numbers to the max, just to watch everything scramble as a giant spider ravages across the map. Spoiler, building our black widow is a bit expensive :p.

TLDR

Mandatory: Archon Continuity, Gloom on the 3rd ability, double umbral + strength and a high trigger stat weapon.
Nice to have: Archon Shards 2 green (stacks), 1-2 yellow for quicker casting and 1-2 red for strength
Gameplay: Press 3+4, jump to a wall, shoot, if not dead then dash with 1, repeat.

Breakdown

This build is focusing on some synergies to deliver one thing, strength, toxic and corrosive damage:
First and foremost being Archon Continuity, giving us corrosive damage basically on top of every damage we do (once we dance around with Silken Stride).
Second we focus on stacking strength, having all 4 abilites profit attack and defense wise from a major increase.

Update: As stated by others, after trial testing it, with our stacking strength we guarantee an orb drop, so we switch Arcane Energize and Umbral Fiber for Equilibrium and now are flexible to switch our second Arcane to either Arcane Arachne for a more of a weapon platform or Arcane Bellicose for even more toxin/corrosive strength with a total of 474% strength.

Synergies

• With the orb drop chance of our 1st ability, Mercy's Kiss, scaling off strength, we make sure that enemies will drop orbs. This will then basically be our guaranteed way of energy upkeep with Arcane Energize.
• Our second ability, Webbed Embrace, will double the damage we do to enemies due to making them vulnerable (not to mix up with armor reduction, this is covered by our continuity mod) with some cc on top, in case something slips through into our "safety net".
• Using the Helminth and substituting our little spiders into Gloom, all conditionals will result in a 132% slow and 19% life steal, making sure no enemies can hit us while we jump around. The aura will also profit form our increased range and the life steal will make sure that our boosted health can stay topped up.
• As the show runner, our 4th ability, Silken Stride, is a major damage and survivability amp. With all conditionals, we profit from a 450% toxin damage increase (all ranged weapons now are imbued with toxin damage + archon corrosive), a 7.52x health pool amp resulting in 14213 HP and toxic explosion that boosts our AOE dmg.

With that HP stack we come down to 20360 EHP, resulting in a nice baseline defense for AOE effects and similar.

Gameplay

Rotation wise, it gets fairly fun and simple due to our double aura abilities:
With our 3rd and 4th ability active, we jump around walls, double our damage by spitting nets, shoot at enemies to do toxin + corrosive damage, dash to elites/high hp enemies once they drop below 50% to execute them, and then jump back to the walls for the safety of our passive and health pool.

Substitutes

Mods:
Depending on the team set up, we could also run Corrosive Projection instead of our aura mod to make sure we strip high SP enemy armor down to 8.2%.
As I've tried to crunch the numbers with range, strength and duration, I figured that the umbral mods just give a great baseline to not lose stats with two sided mods. Only exception is Blind Rage, since it gives us the biggest strength boost ingame.
Stretch and Streamline are interchangeable as they are only for QoL, but especially Stretch is recommended to keep to boost our nets, aura and aoe passive explosions.

Arcane:
Regarding Arcane Energize, having it on level 3 will be also be enough while saving a lot of time/plat.

Helminth
This build utilizes Gloom as a core feature, but I figure Nourish could also be an alternative, there are already some builds out there. We substitute the 3rd abilites, since the upkeep on the spiders is an additional cooldown to keep track off, and I like my builds simple. Also, the spiders damage with pathing sometimes seems to be a drop dps wise.

Loadout

With our arachnid form applying toxin and archon mod applying corrosive, we can profit off often triggering high stat weapons, sticking to the toxic theme I like Bubonico or Incarnon Torid. But since our 4 applies toxic, anything high status will do.
The meele doesn't really matter, since activating Silken Stride will substitute our melee with Mercy's Kiss. When not in arachnid form, we could profit if Harmony's heavy attack ability to quickly trigger our toxin stacks for quick damage.
With our immortal infested friend Panzer Vulpaphyla we make sure that if something goes sideways, our secret agent eats the bullet and we don't drop.

Helminth

For shards I'd recommend to go with two green shards for the full armor strip through more corrosive stacks, one to two yellow shards to increase cast speed of our Mercy's Kiss (depending on how sensitive you are to screen shake/fast movements), and fill the rest with red shards for more damage and survivability.

It's also worth to mention, that the 1st ability grants immunity frames, so [Quickening] the cast speed will shorten those immunity windows too.

That's it, with this being a day 1 build, I would happy to get hear improvement ideas so feel free to comment and besides that, have fun! <3