NOTE: These builds are pictured with a maximum 60% Magnetic bonus.
Basic 0-Forma:
Frustratingly, the Tenet Glaxion has no innate polarities, which makes early builds more difficult to fit. This pictured build takes advantage of the innate Cold to form Viral with just a single Toxin mod. Otherwise, the usual suspects are all included.
One elemental mod and base Cold damage leave very few elemental combo options available. The aforementioned Viral is a great all-rounder, with its near-universal proc increasing damage to Health. The other options, Blast and Magnetic, are significantly less useful. Magnetic is strong against Shields, however very few enemies have truly tough Shields, and you can get it as a Sister bonus anyway. Blast is, in the current meta, practically useless.
Recommended Setups: Viral vs everything, Magnetic vs strong Shields
Hunter Munitions 1-Forma:
One added V polarity and the extra ranks from being a Tenet weapon open up mod options significantly. In this example build I've added Hunter Munitions, which allows the TGlaxion to inflict Slash procs which is normally impossible for it otherwise.
Corrosive 1-Forma:
You can finally properly experiment with other elemental combos now as well.
Corrosive is a great option, with its armour-reducing proc and its great multipliers against Ferrite-armour and heavy Infested units. It combos nicely with the innate Cold, which has an above-average multiplier against Alloy-armour, the other main type of armour, as well as Shields, against which Corrosive is not very effective.
Radiation is the other option to consider, with the strongest multiplier against Alloy-armour. Its proc can be useful as a distraction for enemies, but does not directly make enemies weaker. It is also one of the other possible Sister bonuses. Indeed, with a Radiation bonus (or a later mod), you can have Corrosive and Radiation together in a near-universal anti-armour build.
Recommended Setups: Viral + HM vs everything, Corrosive vs Ferrite-armour, Infested, Radiation vs Alloy-armour
3-Forma:
Two more added Forma and the bonus ranks gives you great mod flexibility, and easy use of the last two slots.
Critical Delay is a solid replacement over Point Strike, offering increased Crit Chance at the cost of some Fire Rate. This can be easily mitigated by any +Fire Rate mod. In almost all cases, I would use Critical Delay.
I already recommend (Primed) Shred on pretty much any non-explosive Rifle, and this is especially true for the TGlaxion. Punch Through is almost always great on Beam weapons, but is especially potent on most chaining Beam weapons, as each enemy hit by the main beam will produce chains, drastically increasing anti-crowd damage. The TGlaxion is no different, with high enough Punch Through and dense enemy groups allowing it to hit 12 or even more enemies simultaneously. The +Fire Rate is a solid DPS increase, especially when running the aforementioned Critical Delay.
For overall, uncomplicated damage increases, you could consider Heavy Caliber or Vigilante Armaments. HC is stronger, while VA is cheaper to max and easier to fit in builds. Both become obsolete once you gain access to Galvanised mods and Arcanes.
You could instead look to boost Crit. Argon Scope/Bladed Rounds are decent conditional Crit mods, and both are very easy to trigger with the TGlaxion. Proton Jet has an unusual trigger condition, but boosts both Crit and Status Chances. Hammer Shot is notably weaker, but is unconditional and boosts both Crit Damage and Status Chance.
Finally, Photon Overcharge is absolutely worth a mention for any loadout with Cold damage/procs. It is stronger than the aforementioned Crit options except for Bladed Rounds, and its secondary ability generating additional Energy orbs can be very beneficial for Energy-hungry Frames.
If you want to truly min-max, look instead to a (Primed) Bane mod. The Faction Damage modifier is a separate damage multiplier to most other effects, and notably is applied multiple times to damage-over-time procs like Slash and Heat. This makes it significantly stronger than most other mod options at extremely high levels. That said, I have still yet to encounter content where Faction Damage mods are truly "necessary".
Finally, you could use the extra space for more elemental mods. Again, the innate Cold limits your options, but there is one last possible combo worth mentioning - Viral + Heat. Heat offers a strong damage-over-time proc that reduces armour and stacks with itself very strongly. Unfortunately, the innate Cold biases towards Viral which is undesirable, but this can be mitigated by a Heat bonus or slotting extra Heat mods.
Radiated Reload is unique in that it adds straight Radiation - no element combining required. This also allows otherwise impossible combinations, such as Corrosive (regular mods) + Radiation (Radiated Reload) + Magnetic (Sister bonus) + Cold (innate). The bigger question is usually whether you can afford the mod slot for it or not.
For the Exilus slot, Sinister Reach is the clear top contender for increased beam range, since the TGlaxion's Ammo Economy is already so good. Otherwise, Vigilante Supplies is notable for its very minor Crit increase.
Recommended Setups: see above. Also consider: Viral + Heat vs everything,
Galvanised Mods
Galv Chamber.
Galv Aptitude can be a strong option, depending on build and bonus. It requires three unique procs to beat out Serration, which can be done in several ways. A Radiation/Magnetic bonus coupled with a three-element or Viral + Slash build can do so on its own, with Radiated Reload being notable, and of course other equipment can contribute as well. Unless you are running a very specialised 1-2 damage type build, I think Galv Apt is worth using most of the time.
