Core of Darkness was a project for Wolfenstein 3D, made by MrWolf. It was made circa 2003 and only featured in closed circles, never being fully finished.
The mod was based on numerous John Carpenter movies, with the protagonist resembling Roddy Piper from 1988's They Live.
The mod features a host of new graphics, with the main enemies being hooded monks. New weapons are also featured. Other than that, Atina's shared video clip of the mod still features standard Wolfenstein 3D sprites and other graphics already featured in previous mods. These were most likely placeholder graphics until new ones were better developed.
Similar to Warlock, the mod entered most people's conscience via Atina's playthrough on her YouTube channel.