hardcore dark is a mod that takes care of removing the slightest trace of lighting in your Minecraft worlds, to make night or cave exploration much more complicated and scary than it currently is.
Surely it has happened to you that even in a cave without torches you can feel things around you, regardless of the gamma setting. Well, this mod takes care of eliminating the light coming from the sky, as well as the lighting of the blocks and the lighting distance of the light sources.