Discharge a rail of ionized death or throw the Ferrox like a spear and create a localized field of attraction no enemy can escape from.
The Ferrox is a Corpus Spear Gun introduced and wielded by Index broker Derim Zahn. Its Alternate Fire tosses the Ferrox as far as 50 meters, creating an electric field where it lands and pulling enemies towards it. It is available for research in the Energy Lab of a Clan Dojo.
The Ferrox's alternate fire throws the weapon itself at the target, and upon landing on a surface arcs of electricity will emit from the Ferrox and chain to any nearby enemies, dealing 150 Electricity damage every 5 seconds with a high chance to proc. Enemies under this effect will also be passively dragged towards the Ferrox.
The Ferrox will remain at the location where it was thrown for ~20 seconds after landing, automatically teleporting to the player after said duration or until the player manually picks the Ferrox back up for use again.
Throwing the weapon does not consume ammo.
The Ferrox's alt-fire has a max throwing range of ~50m (though it may be displayed as slightly less due to the forward movement of the player when throwing the weapon).
The arc Ferrox will take when thrown is affected by both the angle of the throw as well as how much the throw was charged.
Enemies killed by the primary or damage from the secondary attack will vaporize, similar to channeled kills by melee weapons. This makes it very viable for stealth, as long as the weapon is silenced or Hushed Invisibility is used.
Keep in mind that there is a long-standing issue with silenced weapons and/or Hushed Invisibility that causes some enemies to not count as stealth kills despite being unalerted when killed. So you will often lose your stealth bonus if trying to use this vaporization feature as a way to level the weapon up through stealth.
Fire rate appears to increase the chance for the alt fire to deal damage to tethered enemies, so increasing fire rate will increase the DPS on this fire mode slightly.
The damage can be increased by base damage mods like Heavy Caliber or faction-specific damage mods (e.g. Bane of Corpus), increasing the effectiveness of this fire mode.
This weapon's decent critical chance and damage multiplier make critical builds using Point Strike and Vital Sense good options.
When applying additional elements to the Ferrox, its alt-fire will proc them periodically; as with other weapons with an elemental base, Electricity will be applied last if there are two or more other elements modded for, unless an Electricity mod is included in the order.
Heavy Caliber has a marginal effect on the Ferrox's primary fire even at long range, making it a viable mod for increasing the weapon's damage output.
It does affect additional shots when using multishot mods such as Split Chamber.
Tactical Reload has an effect while the spear is out after alt-fire is used, so it's possible to do seamless reloads this way.
The Ferrox's alt-fire is very useful as a crowd control tool in Survival missions, as its tethering arcs may stun enemies with Electricity procs and also pull them together in a close lump.
This tethering effect is further amplified on corridors where enemies pass through frequently.