In a previous post, I partly in jest explained why young Tom Riddle could be my HP spirit character. I was ditraught to learn that post caused mental/emotional harm to an HP fan. This did spawn a wonderful creation by my lovely cousin: Tom Riddle(ness). I don't know how she would define it.
Here's my take: a drive, act or manner of behavior that is evil with no regard for anything else besides the gain, joy, or delight of the actor.
I welcome her take and defer to her opinion as the creator of the word and its visual presentation.