Its origins derived from certain hardcore hip hop and gangsta rap artists, such as the Geto Boys, who began to incorporate supernatural, the occult, and psychological horror themes into their lyrics.

While exaggerated violence and the supernatural are common in horrorcore, the genre also frequently presents more realistic yet still disturbing portrayals of mental illness and drug abuse.

Horrorcore defines a style of hip hop music that focuses primarily on dark, violent, gothic, transgressive, macabre and/or horror-influenced topics such as death, psychosis, psychological horror, mental illness, satanism, self-harm, cannibalism, mutilation, suicide, murder, torture, drug abuse, and supernatural or occult themes.

[9] The following year saw the release of Boomin' Words from Hell, the debut album of Detroit-based rapper Esham, who would become particularly influential on Midwest horrorcore (though he rejects the term, preferring "acid rap").

Nonetheless, Kool Keith brought significant attention to horror-influenced hip hop with his lyrical content as a part of the Ultramagnetic MC's and his 1996 debut solo album Dr. Octagonecologyst.

[13] The Geto Boys' 1991 album, We Can't Be Stopped, was also influential on the horrorcore genre and contained themes of paranoia, depression, and psychological horror, especially in the track "Chuckie", and "Mind Playing Tricks on Me".

[18][19][20][21] The Flatlinerz and Gravediggaz, along with the Geto Boys, Insane Clown Posse and Kool Keith, remain the most important artists in the development of horrorcore as a specific genre.

Bone Thugs-N-Harmony's E. 1999 Eternal, released in the same year, contains tales of the occult throughout, specifically on songs such as "Mr. Ouija 2", "Mo' Murda", "East 1999", and "Da Introduction".

Horrorcore is generally not popular with mainstream audiences, though in some cities, like Detroit, it is the dominant style of hip-hop, with Detroit-based performers such as Insane Clown Posse[22] and Eminem,[23] as well as Twiztid, having been commercially successful throughout the US.

[27] In September 1996, Joseph Edward "Bubba" Gallegos, an 18-year-old from Bayfield, Colorado, killed his roommates after ingesting methamphetamine and listening repeatedly to horrorcore rapper Brotha Lynch Hung's song "Locc 2 da Brain".

[28] Gallegos was said to be a massive fan of Brotha Lynch Hung and his minister suggested that the music played a role in the killings, although he provided no evidence to back up that claim.

[31] Allegedly horrorcore-related criminal activity has, in rare cases, even included ad-hoc domestic terrorism, such as when a Juggalo-led terrorist cell calling itself the "Black Snake Militia" attempted to raid a National Guard armory in 2012.