Kuva (Resource)

"A mysterious red fluid coveted by the Grineer Queens."

- In-Game Description

Kuva is a rare resource that can be extracted with Operators help from Kuva Siphons, that appear in high-level Grineer missions after completion of The War Within quest.

Successfully destroying one Kuva Siphons will grant from 600 to 700 Kuva, while failing only around 200 at best.[requires more testing]

In addition to its use as a crafting material, Kuva is used to randomize Riven Mods.

Blueprints Requiring Kuva
Click to view the Blueprints requiring Kuva 

Lore
It's implied several times by Teshin that Kuva is the blood of long slain Orokin. This idea is reinforced by the Elder Grineer Queen saying that she is Orokin and they "made you" (referring to the player's Operator). The Younger Queen also begins to harvest Kuva at a higher rate after the Elder Queen's defeat, saying that it will bring her back to life further backing up this Orokin Blood theory.

How the blood can have conscious of Orokin tied to it is unknown however.

Teshin also states that some believe Kuva is a poison that corrupts, which may also be true, as the hatred of the Tenno's betrayal (or the evil of the Orokin themselves) are embodied in the Kuva, corrupting those who consume it with the same hatred and evil.