This build is centered around maxing out our range for the sake of catching ALL the enemies in our web with Larva while obtaining just enough power strength to hit the 90% damage reduction threshold for Parasitic Link. Range also affects the distance we can travel from our Parasitic Link, so it allows a much more mobile playstyle than the standard strength build. We also want base or lower duration so that we don't get stuck waiting for ages for our Larva to expire whenever we grab enemies through walls with it. With this setup, our Larva lasts 5 seconds, which is time enough to kill, but feels short enough not to be annoying when we have to wait briefly on its expiration. Additionally, because we're keeping our power strength at the bare minimum, it is MUCH easier to build stacks on lower health targets than it is with a max strength build. I personally prefer being nigh invincible over doing more damage with Nidus' abilities - the killing comes from weapons such as a Zaw with Exodia Force or the standard AoE weapons like [Kuva Bramma] or [Kuva Zarr]. Pick your poison for what you like to kill them with, then change out your 2nd arcane to revolve around it.

Arcane slot 1 options:
Arcane Grace - honestly just too convenient not to use. You do not want to rely solely on your 4 for [Regen]. I'd say this is mandatory, though you can use a lower rank if you cant get R5

Arcane slot 2 options:
Arcane [Guardian] for additional damage mitigation if you feel you need it. This increases [Nidus]'s effective HP from 40,910 to 85,530
Arcane Avenger for additional crit chance across the board, this is a good option if you want extra damage, but don't care to swap out this slot often
Arcane Acceleration for killing with primaries such as the [Kuva Bramma] (and god does this arcane make you a destructive force with this weapon)
Arcane Strike if you prefer to kill with melee, especially if using Exodia Force

Optional Changes (same polarity configuration): Convenience changes you can make by switching auras or reducing [Adaptation] rank.
Variant 1: Swap [Corrosive Projection] to [Enemy Radar] if you need radar and don't trust your pet not to die
Variant 2: Swap [Augur Reach] for [Teeming Virulence] for more primary crit chance. We will need to swap [Adaptation] to R8 and [Rage] to R2 to afford the capacity (or use [Steel Charge])

Budget Options (that require less forma):
Option 1: Keep aura and exilus slots as default and swap [Corrosive Projection] for [Steel Charge]. This build requires only 2 forma.
Option 2: Keep aura and exilus slots as default, swap [Corrosive Projection] for [Steel Charge], and use R4 [Adaptation] without polarity. This build requires only 1 forma.

Optional Changes (that require additional forma)
Umbral Arachnidus: My original build was made with the rarity of Umbral Forma in mind, but if you're okay with using one, you can swap [Augur Reach] to Umbral Fiber (forma'd), Power Drift to Cunning Drift (forma'd) to increase effective HP from 40,910 to 93,550 (149,720 w/ Arcane [Guardian]) at the cost of 15% range. Additionally, if you reduce [Rage] to R2 and add an aura forma, you can swap Auras at will with this build without being concerned with capacity.

This is my first build upload to Overframe, but I've gotten a lot of questions around how to build Nidus so I figured I'd put something here to point people toward. Please let me know how I did - open to any constructive feedback. Also let me know if you'd like to see separate builds for optional changes. Thanks!

(Update 6/10/22: Added builds for variants 1 & 2 and created a separate Umbral Arachnidus build using different polarities, but revolving around the same playstyle.)