From Destinypedia, the Destiny wiki
Blight (also called Taken Blight) is a radiating substance of sterile neutrinos emitted by the Taken. Blight appears when Taken are nearby. When generated it takes the form of either a mist that blankets an area, or stationary spheres of Darkness.
Blight resembles a black liquid or vapor, usually crackling with energy and exhibiting the same eerie luminescence as the Taken themselves. It can flow across the ground like a viscous fluid, seeping into the soil and presenting a contamination hazard when it comes into contact with water supplies. It can also collect into floating spheres, themselves known as Blights, which can be used as shield generators, interdimensional communication terminals, or portals to the Ascendant Realm.
Blight is a clear indicator that Taken enemies are either nearby or about to be summoned. When this happens, the Blight will take its mist form. When the Taken appear, Blight may appear in its sphere form along with them, or the spheres will be around when a player enters the area. While its mist form is harmless, spheres of Blight generate a field within a short area around it. When players get inside that field, the debuff Shadow Touched is applied. This effect slows a player's movement speed, prevents sprinting and any double jump ability, and disables recovery. The only way to counter the debuff is to destroy the sphere with any weapon or ability equipped. Once that is done, all negated abilities return. At least one sphere appears in any activity where Taken are present, the exceptions being Patrol and the King's Fall raid.
In the boss fight of the strike Blighted Chalice, Malok, Pride of Oryx regularly summons Blight spheres along with waves of Taken close to each one. The spheres are spread out along the Shrine of Oryx. In addition to having Taken spawn close to each sphere, Malok's powers increase the Blight's range. Each sphere covers a large portion of space, allowing the Blight to cover the entire battlefield. Until a sphere is destroyed, the Shadow Touch effect will be active everywhere, making it difficult to move around. As mobility is needed to target Malok and avoid enemy attacks, destroying at least one the blight spheres is a priority.
In Destiny 2, some Blights have a shield and some of the shielded Blights, rather than applying the Shadow Touched, will minorly, yet rapidly damage a Guardians health. Some aesthetic Blights, such as the ones in the Ascendant Realm, will deal high damage or insta-kill a Guardian.
Blights must also be destroyed during the Taken Blight Public Event.
List of appearances