Flatlinerz is a horrorcore group from New York City. They are responsible for introducing the term “horrorcore” with their 1994 release U.S.A. (Under Satan’s Authority).
The group is Redrum (Jamel Simmons, nephew of Russell Simmons) and two other emcees: Gravedigger and Tempest. FLM was an extension of the Flatlinerz (Flatline Massive) which included artists Butter, Mayhem, and OMN999 (Omen).
Def Jam targeted the Flatlinerz as an alternative to Gangsta Rap, which was dominating hip hop music at that time.