This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Strzyga (Slavic)
Strzyga is usually a female demon in Slavic mythology, which stems from the mythological Strix of Ancient Rome and Ancient Greece. The demon is similar to a vampire, and is predominantly found in Polish and Silesian folklore.
When a person believed to be a strzyga died, decapitating the corpse and burying the head separate from the rest of the body was believed to prevent the strzyga from rising from the dead; burying the body face down with a sickle around its head was believed to work as well.