Lucifer means light bringer, or something similar. When he (or they) interbred with humanity, he gave them the ability to intellectually conceptualize his experiences. Before, humans were essentially guided by an intuitive understanding of life. They were one with their environment.

This was a necessary stage in humanity's spiritual evolution that allowed for the individualization of souls and the development of free will.

I need not detail the dark side of these developments, for they are plain as day when one examines human history and modern society.