HELP I FOUND THIS SIGN ON

Is your friend religious?
Cos' if so,he might had drawn the symbol on the book and told you he didn't do it.You would research the symbol and find out it was a Demon's Sigil.
Then your friend will tell you all the Greek Gods and Mythology might be connected to the devil.

OR:

He simply wanted to make a joke to you.

Consult a priest or find a spell that protects you from demons. That type of demons are to hard to get rid of by magick. If you experience any paranormal activites PM me. I had sent a Evil Incubus away cause he was preying on my Sister.