Arachne Gorgon

Known as "The Heretic" witch, Arachne becomes the main antagonist in Soul Eater after Medusa takes on the form of a little girl. She is the leader of the massive Organization "Arachnophobia" and is referred to as the mother of all Demon Weapons. She is Medusa's older sister. She is the eldest of the three Gorgon Sisters. She created a Demon Weapon by killing off humans and killing a witch. Her animal theme is the spider. She can create thread that leaves a person immobilized for an unknown amount of time (it depends on how strong that person is).

(Source: Wikipedia)