Tommyknocker

The Tommyknockers are a mysterious alien race in Stephen King's The Tommyknockers (1987). In the novel and live-action mini-series, The Tommyknockers crashed on Earth thousands of years ago due to a fight between the pilots of the ship for reasons unknown. They somewhat resemble a tall fusion of a human and a grey alien with a dog-like face. The back of their heads are stretched from the back, implying the aliens high intellect, and spikes protruding from the shoulders.

Abilities
One thing that the Tommyknockers possess is an infectious green gas that causes a long and painful transformation into a Tommyknocker called "The Becoming". It is because of this gas that many people over the years who've lived near the crash site go insane and harm or kill innocent people or each other. The symptoms include heightened intelligence, teeth becoming loose from the gums, moist, dead skin that when taken of reveal skin to that of a Tommyknocker, and even affects people mentally by having them believe the Tommyknockers bring the infectious gas as a gift to man as the next stage in human evolution, similar to the Reaper indoctrination process in the Mass Effect series.