Forma

"This shape-altering component is fundamental to Orokin construction."

- In-Game Description

Forma is a resource used to add, remove, or alter the Polarity of a Mod slot on Warframes, Archwings, weapons, or Companions; add Tiles to a Clan Dojo; to rise in Syndicate ranks or serve as a component in the creation of certain weapons and items.

Two Forma are required to build an Exilus Adapter.

Acquisition
Forma or its blueprint can be: &#42;Note that the blueprint is consumed when the Forma is crafted.
 * Purchased in the market for or  for a bundle of 3 Forma.
 * Received as a Daily Tribute.
 * Blueprint received as an Alert Reward.
 * Blueprint offered as Invasion battlepay.
 * Blueprint can be found in Void Relics.
 * Blueprint received as a reward from Orokin Derelict Defense.
 * Built/Blueprint can be received after obtaining all three caches in Earth Sabotage.
 * Blueprint received as a reward from Arena missions.
 * Found in Reinforced Orokin storage containers in Orokin Derelict and Orokin Void missions.
 * Blueprint received as a Conclave end-of-match reward.

Using Forma on Equipment
To apply a Forma, go to the Arsenal and access the desired item's Mod loadout. Select Action at the bottom of the screen, then choose Polarize, which will show a layout of the item's mod slots and polarities. Click on a slot to cycle through the possible polarities. A slot that already has a polarity (either by default or from a prior polarization) can also be changed.

Forma can only be used on equipment that has already been ranked to 30 and, when used, said equipment is reset to rank 0 (unranked). Warframe skills are also reset, with skills and their respective ranks needing to be re-unlocked. Forma can be used again on already polarized equipment, provided that it is leveled to 30 again. Orokin Catalysts and Orokin Reactors are unaffected by the usage of Forma. Re-leveling equipment after using Forma on it does not grant mastery points.

For each Forma used on equipment, said equipment will gain a star above the name of the equipment starting from the center.

Blueprints Requiring Forma
Click to view the Blueprints requiring Forma. 

Trivia

 * Forma means "shape" in a variety of languages.
 * From the Scanner inside the Orbiter, one can occasionally hear a Grineer inspecting someone's cargo and getting bribed with a Forma after he finds something suspicious.
 * The prevalence of golden surfaces in Orokin Void levels and on Prime equipment may indicate the use of massive amounts of Forma in their construction. The grey surfaces in the Clan Dojo may be due to Tenno improvising with more mundane materials while copying Orokin aesthetics.
 * A Forma is required to craft nearly all Clan Research weapons, though this is most likely only for gameplay reasons as most of them don't involve any Orokin technology.