Gangsta Nip or esham probably should be considered the origintors of horrorcore.
Horrorcore was bomb back in the day now its just a bunch of fuckin retards...but good horrorcore to me is like lynch or Spice like good ghetto/gangsta tales wit a more dark tone to it, cuz that shit more realistic to me, or shit that shows you the horror of the system we live in like gravediggaz, or DOC's Helter Skelter album , or even Dr. Dre's and Cube's Natural Born Killaz. That shit is actually outstanding horrorcore rap.
I don't like mufuckas who rappin but seem like they would've just been into Slayer if horrorcore rap wasn't around.