Build it. It is a straightforward Corrupted Holokey purchase rather than a Sister hunt, and the charge-fire plus pulling alt fire covers both single targets and groups. The tradeoff is a small 20 round magazine and no punch through, so ammo economy needs attention.
Alt fire throws the spear to create a 10 meter field lasting 30 seconds that deals Electricity damage every 2 seconds while pulling enemies together for follow-up hits.
Tenet Ferrox is the Sister-tech remake of the Corpus speargun Ferrox, but unlike most Tenet weapons it is not a Sister drop. It is bought directly from Ergo Glast in any Relay using Corrupted Holokeys earned from Void Storm missions.
It stays talked about in 2026 because the charge trigger can be held down to keep firing consecutive shots almost like an automatic weapon, and the alt fire’s pulling field is genuine crowd control rather than just extra damage.
Styanax’s passive, which boosts weapon critical chance from his shields, applies double to spearguns like this one, giving it a niche synergy pick some squads build around.
How to get the Tenet Ferrox
- Farm Corrupted Holokeys in Void Storm Railjack missions (the Railjack fissures); each Void Storm has a chance to drop a stack.
- Visit Ergo Glast, the Perrin Sequence representative, in any Relay and buy the Tenet Ferrox for 40 Corrupted Holokeys.
- His stock rotates every four days at 00:00 UTC, one copy of each weapon per rotation, and each rotation rolls a new bonus element and percentage. Wait for the roll you want or buy now and fuse later.
The Mastery Rank gate is enforced on store-bought Tenet weapons. Valence Fusion merges two copies up to 60 percent and lets you pick the element. Rank 40 with five Forma.
Stats
| Class | Primary |
|---|---|
| Mastery Rank | 16 |
| Trigger | CHARGE |
| Noise | Alarming |
| Fire Rate | 2.67 |
| Accuracy | 16.7 |
| Magazine | 20 |
| Reload | 1.8 s |
| Critical Chance | 34% |
| Critical Multiplier | 3x |
| Status Chance | 26% |
| Riven Disposition | (1.15) |
| Damage | 200 total |
|---|---|
| Impact | 20 |
| Puncture | 140 |
| Slash | 40 |
Riven disposition is 1.15x, near the middle of the pack. Not a priority riven target since the alt fire’s crowd control carries the weapon more than raw stat rolls do.
Builds
The charge-fire’s 34 percent crit chance at a 3x multiplier supports a hybrid build: crit mods for burst damage on groups pulled together by the alt fire, plus multishot and an elemental combo tuned to the current progenitor roll.
Rifle
Rifle
Rifle
Rifle
Rifle
Rifle
SET: PRIMARY
Rifle| Mod | Why it’s here |
|---|---|
| Serration | Flat base damage increase for the charged shot. |
| Split Chamber | Multishot, more explosive pellets per charge and per pull-field tick. |
| Point Strike | Pushes the weapon’s already strong 34 percent crit chance further. |
| Vital Sense | Adds critical damage on top of the weapon’s native 3x multiplier. |
| Galvanized Chamber | Adds multishot, and every kill stacks more multishot for a while. |
| Primed Cryo Rounds | Adds Cold damage, useful for a Viral combo against tougher targets. |
| Hunter Munitions | Critical hits have a chance to add a Slash proc, bleed damage that ignores armor. |
| Primed Shred | Adds fire rate and punch through so shots pass through the first body. |
Primary Merciless is the top pick, stacking flat bonus damage per kill up to 12 times. Primary Deadhead is a strong cheaper alternative for players who land headshots with the charged shot.
Reviewed September 2026.
Pros and Cons
Pros
- Bought directly with Corrupted Holokeys, no Sister hunt required
- Charge-and-hold fire acts like a semi-automatic heavy hitter
- Attraction Field alt fire groups enemies for follow-up damage
- High native crit chance and 3x multiplier suit a crit build
Cons
- No punch through, unlike the base Ferrox
- Untradeable, so a bad progenitor roll means waiting for the next 4 day rotation
- Small 20 round magazine paired with a 2.67 fire rate strains ammo
A good pick for players who want a strong Tenet weapon without the Sister hunt grind, and who like alt fire crowd control over raw punch through.