Components
Adra Mutagen: Grants the best resistances of the mutagens. Also happens to be the easiest to get, but the resistances are pretty irrelevant on the scope of an unkillable pet so just choose the one you like the look of.
Desus Antigen: You MUST use this one if you want it to be a 0 forma build. You need the Vazarin (D) polarity for [Calculated Redirection] it's the only way to fit everything without using lower levels of mods.
Vulpaphylas are uniquely one of the very few companions able to utilize both Tenacious Bond AND Reinforced Bond efficiently. Sentinels (besides [Wyrm] Primes) and normal Kavats need a frame with really high shields to use shield link for [Reinforced Bond] to trigger (or abuse the synth mod reload thing which is equally load out restrictive and annoying to monitor and keep up). And for [Tenacious Bond] Kubrow companions need to equip [Bite] AND [Hunter Synergy] which you can only get from Ghoul Purge or Plague Star plus it's pretty buggy when it comes to triggering Tenacious Bond's requirements. And Sentinels/Moas need to equip guns that are otherwise unpractical since the normal primer/tagging weapons like [Helstrum] just won't hit the threshold.
Vulpaphylas though have enough base shields to hit the 1200 threshold with [Calculated Redirection] AND the same base crit as other kavats so you only need a rank 4 [Bite] to get exactly 50% crit on them! Not to mention they have other pieces of utility that are hard to come by or are only brought by them!
[Viral Quills]: Just as useful now as it was before. Mini [Saryn] spores that help by spreading viral around to everything and tags them for [Synth Deconstruct] or alternatively gives you a solid amount of healing if you opt for [Hunter Recovery].
Panzer Devolution: Oh wow cool! The new update allows companions to not die? That's great. Their new 9 capacity mod + [Medi-Pet Kit] will be doing what this 3 capacity mod has been doing since it was released. Jokes aside despite how amazing the new mods and companion durability are; I see no reason to swap to the new mods specifically on a panzer build when ol' reliable still does the exact same thing and you get it just by making a vulpa. And something that's very unique to the devolution mods is that you actually don't lose the effects of [Tenacious Bond] or [Reinforced Bond] when your vulpa gets downed as where literally any other companion loses these buffs while they're downed.
[Martyr Symbiosis]: Generally just good. It's basically just [Sacrifice] except it's much more readily available and actually works at the cost of being less powerful of an effect.
Mod Ranks
I thought I'd just touch on this to explain my reasoning. Essentially [Fetch] is only rank 4 instead of rank 5 because it's a super common mod and is extremely cheap to rank up so it's just generally more convenient to use have a copy tailored to this build in that slot than to go get another [Martyr Symbiosis] or other rare mod instead. Rank 4 [Fetch] is literally 1 less meter of [Vacuum] and ironically enough that's still a larger radius than the [Vacuum] mod for robotics.
[Calculated Redirection] is only rank 9 instead of rank 10 because I honestly cba to spend like 5k endo and 250k creddits on 80 more shields when I'm already hitting the threshold for the buff. If you care enough then go ahead and make it rank 10 it literally doesn't matter since it's on a polarized slot meaning 13 and 14 cost are both reduced to 7 anyways.
It's worth noting that if you drop [Animal Instinct] for another lower cost mod, like another utility bond mod or [Hunter Recovery] or whatever else, you can use a rank 5 [Fetch] but I don't think it's worth the qol IMHO. 1 meter will never be noticed. That being said if you want to slot Primed Animal Instinct into the build you'll have to use 1 forma for a - polarity. And if you do that you can also use a rank 5 [Fetch] even with Primed Animal Instinct.
It's NEVER worth ranking Bite up past 4 imho. You get exactly enough crit at rank 4 for kavats/vulps to trigger [Tenacious Bond] and your companion wont do meaningful damage even if you had a max rank Bite not to mention the obscene cost of leveling/maxing it paired with how awful farming for it is and how much mod space it takes up.. just don't. Keep it at the minimum level necessary.
Hope this is useful! I know it's not SUPER new player friendly because of some of the mods requiring some effort to get, but it's a 0 forma build that someone can passively work towards without having to dump precious early forma into a pet. Or if you're like me and having a million things you're trying to forma and are patiently counting down the days till Plague Star next week.
