Originally, Tou Mu was created by the Scarlet Queen and the Ebon Dragon to punish the unmerciful and the arrogant. She fulfilled her mandate until she learned how to draw chi from the suffering of her charges. Instead of simply punishing vices, Tou Mu instead went to inspire them, mapping the territories of hatred, greed, and lust in the human heart, only to take them captive into her Hell once they died. As such, Tou Mu was one of the more powerful Yama Queens early on.
When the Wan Xian were created, Tou Mu suffered the most under them. The Ten Thousand Heroes targeted her the most and even defeated her when she fought them manifested in the physical world. Bitterness and anger against the champions of Heaven gnawed at her and she withdrew during much of the late Third Age to consort with dark creatures that might aid her. During the Fourth Age, Tou Mu became active again. For example, she corrupted Shau-yar Han by showing him the Outer Things she had found during her absence. She controlled a vast army of the dead, and particularly enjoyed torturing the Kuei-jin, as she was a great enemy of the Wan Xian. Her hate against Kuei-jin is strong enough that she does not tolerate them as akuma servants, although she is not above making deals with them.
During the Fifth Age, Tou Mu appeared again to be one of the leading Yama Kings in the race for the title of Demon Emperor. Her most extraordinary feat was the corruption of the leaders of the Jade Court. She also made an alliance with Ghost-Killer, the first leader of the Righteous Devils of Kowloon.
In one of the scenarios of Ascension, Tou Mu is ended when she agreed to join her power to that of the Awakened necromancer Voormas via a tantric ritual, who instead devoured her essence and used it to enter the Apex of History.
In one of the scenarios in Time of Judgement, Tou Mu has the possibility to become the Demon Empress in "Serpent Bites the Hand".
Across the ages, Tou Mu has always manifested in the same form: A woman with eighteen arms clad in an iron armor, the hands in taloned gauntlets and her face concealed by a horned iron mask. Three eyes blaze under it and she has numerous regalia that resonate with dark and tainted power.
Traditionally, Tou Mu is associated with space and the stars and her servants often use these symbols as signs of allegiance.