A Strega is a practitioner of Italian folk magic. They're first seen in Blood Rites.
They specialize in divinations, love potions, fertility blessings, and protections. They can also do a pretty vicious set of curses with a technique called the Malocchio. The Evil Eye. 
In the series Edit
- Main article: Blood Rites
In Blood Rites, someone is targeting the women around Arturo Genosa using an Entropy curse.
The streghe are the ex-wives of Arturo Genosa: Madge Shelly, Lucille Delarossa, and Trixie Vixen. They are led by Lord Raith for his own purposes to get Genosa back in line.