In the very beginning Shashi was only a miko for Ashuraou along with her sister Kara but well it seems like being a miko for the great warlord wasnt good enough. So later she got married to Ashuraou and became his wife. But it still wasnt good enough for her so during the Holy War she helped Taishakuten in his rebellion by telling Taishakuten all the secrets of the Ashura clan so he could win. She betrayed Ashuraou and his whole clan which was why they all got wiped out. She became Taishakutens wife quotEmpressquot Shashi. Shashi gave birth to twins one being Taishakutens son and the other being a child of the Ashura clan Ashuraous child. So she tries to kill her own child Ashura with her own hands. source: Nishis RG Veda Gallery