Catalysts, Reactors, and Forma
Once you’ve really gotten attached to a specific weapon or Warframe you might want to upgrade it more than its current Capacity allows. The good news is that there are items which double every piece of equipment maximum Capacity permanently. The bad news is that they’re hard to come by.
These items are called Orokin Catalysts and Orokin Reactors. They’re both essentially the same thing, except that Catalysts are applied to weapons, while Reactors are needed for Warframes, companions, and Archwings (Warframe’s equivalent of spacebound jetpacks).
Sadly, there’s no guaranteed way to acquire either add-on. You can earn them wholecloth or as blueprints from things like time-limited Alert and Invasion missions, from special in-game events, daily login bonuses, or as a random reward in Sorties. That’s… pretty much it.
Another downside is that Catalysts and Reactors can’t be removed, which means no sharing just one of them between whatever equipment you switch to. Make sure that if you apply one of these rare items you’re absolutely certain you want to upgrade the gear in question. One helpful rule of thumb is to save them for Prime versions of existing weapons (e.g. the Soma Prime instead of the Soma). That’s because you typically want to sell weaker versions of weapons once you get their upgraded versions, as it opens up valuable inventory slots.
Forma
Bumping up an item’s maximum capacity isn’t the only way to increase the quality and quantity of Mods you can equip to it. Polarities themselves can also be added and changed according to the user’s whims - assuming, of course, that you have enough Forma.
Forma is a semi-rare resource that often comes as just a blueprint - similar to Catalysts and Reactors. You can earn those blueprints from Void Fissure missions the same way as Prime parts (once again, you can check out our Warframe Crafting guide for details on Prime parts and Void Fissures).
Forma is also given out for completing certain objectives in the Orokin Derelict and Orokin Void zones. Unlike Corrupted Mods, however, Forma doesn’t come from any special side objectives. You’ll just get it in the regular course of completing those missions. Or you won’t! That’s the joy of randomized mission rewards.
Forma, once earned or crafted from blueprints, is used in a variety of ways. Certain weapons need it as a crafting material. Player-owned structures, called Dojos, use it in the construction of new facilities. For the purposes of modding, however, a single Forma can add or change the Polarity of one Mod slot on any piece of equipment.
This obviously has the benefit of letting you to use more numerous and more powerful Mods on equipment, since matching Polarities cut Mods’ Capacity cost in half. “Forma-ing” an item does have a downside, though. Doing so will reduce the affected item’s level back to zero, so you’ll need to take that gun, melee weapon, Warframe, or companion back with you on missions to grind experience points all over again.
