Avery Cooper - The Last Eclipse

Darkness - 'a lack of illumination, an absence of visible light, or a surface that absorbs light, such as black'

The fear of darkness is not being alone in the dark, its the fear of NOT being alone in the dark. Darkness isn't an unusual thing anymore, you learn to adapt. At least, you have to anyway. Light is the only thing keeping them away, keeping us safe. Without it... id hate to imagine.