Eye of Thoth

The Eye of Thoth is an ancient Egyptian symbol of protection, royal power and good health. It first appears in Grave Peril.

Description
According to Bob, the Eye of Thoth is quite a popular occult symbol, used by a number of people ranging from occult groups members, tv personalities and comic books heroes.

Death Masks
In Death Masks, Butters and Dresden discover a tattoo on the arm of an unidentified corpse in the morgue, about a square inch wide, drawn in faded green ink, which Bob later identifies as an Eye of Thoth.

Later, Father Forthill shows he has one tattooed on his own arm, which he got along with a number of other priests ordained at the same time, Father Vincent included, who pledged to deal with some of the more gruesome supernatural creatures and their activities at the time.