Do you believe in God? If yes, then you kinda have to believe in Satan too. If you don't believe in God, then I wouldn't see why you would think there was a devil. It all depends on your beliefs really.
My god RAH is the sun god. He grows my food lights my day and warms me up. I can see him. I can feel him. Hes right there. Jesus and the christian god dont have a thing on RAH. I can point to my god. Christianity is a faith that must be believed in like the easter bunny or the great pumpkin. As far as i can tell the devil or satan was invented to scare you into believing in the faith by telling u that you will burn in a lake of fire for eternity. Man thats a LONG time. Why is your god so mad at me for my disbelief. He sure does want me to suffer. Think about it.