Editing VGO's Guide to Warframe (section)

===Riven Mods===
Riven mods are a special type of mod. When you get it, it will be "veiled," which means that its properties are hidden, other than for the general type of weapon that it's for, such as shotgun, rifle, secondary weapon, or melee weapon. To unveil a riven, you have to do a task with the riven equipped in a weapon that you're using. The task can be something like "kill 10 enemies while sliding" or "kill 5 dargyn pilots before they hit the ground with a dragon key equipped."
Once unveiled, the riven will be for a specific weapon, like a Boltor, and will have 2-3 random positive stats and may have a negative stat as well. You can use kuva to reroll the stats on a riven, although the cost goes up with each reroll.
Rivens also have a disposition, based on how popular the weapon is. The more popular the weapon, the lower the disposition, and the lower the stats of the riven. (That means that a Zhuge riven may have better stats on a base Zhuge than on the Zhuge Prime.)
There are some tricks to make unveiling rivens easier. Here are a few. [[Unveiling_Tricks]]