Gorgon

The Gorgons were a race of humanoids that entered human Greek mythology, as their name suggests. One gaze from the Gorgon's eye and the person will be turned to stone (which is similar to Petrifold Regression). (SJA: Eye of the Gorgon)

Biology
The Gorgons could possess people, but in reality they look like ethereal serpents. Once a Gorgon finds a host, it can expand the host's lifespan.

History
Three Gorgons came to Earth three thousand years ago via a strange talisman. One was killed by a greek hero, one slain by a professor and his wife in 1959, but there was one surviving one. This Gorgon disguised as an abbess and formed a sisterhood of nuns to protect it. Since then, it has sent the nuns to find the talisman so it can escape Earth. (SJA: Eye of the Gorgon)