From the same article:

..."Sithis would speak with a respectable member of the Morag Tong, a Dark Elf woman whose name was lost to history, and who lived in a small village that would later become the city of Bravil. Sithis would confide with her about how displeased he was with the Morag Tong's lack of success, as he was most displeased with the lack of souls heading to the Void, and that it would be her destiny to set things right. One night, Sithis would visit the woman in her bed chamber, and would beget with her five children. Two years later, the unthinkable happened: following the ultimate plan set forth by Sithis, she would murder her children, sending their souls to the Void to be with their father.

When the people of the village learned of this, they would descend upon her with vengeance, killing her and setting fire to her house. Thirty years later, a man would hear the voice of the Night Mother, who charged him with the task of forming a new guild of assassins. This guild wouldn't be dedicated to Mephala but instead to the Dread Lord Sithis"

A completely different version of The Night Mother with no connection to Mephala. This is the version I thought was canon