The Joro-gumo is a spider-woman, but she's not a member of the Avengers with a needlessly complicated backstory. She's a giant spider, with the ability to take the form of a beautiful lady (sometimes the top half is human, and her lower torso is that of a spider) who seduces men, wraps them up in her webs, poisons them, and eats them. One variation of the Joro-gumo myth says that sometimes she appears as a woman holding a baby, who asks men passing by to hold it. When they do, they are someone surprised to discover the "baby" is made up of thousands of spider-eggs, which burst open.
