Mahishi is the elder wife of a king in ancient Hindu kingdoms. In ancient and medieval periods, a king had many wives, who were not treated as equals. The knowledge texts recognize them with different titles. The senior most of the wives was called mahishi, and she was also known as pattarajni.
The recognition as Mahishi had religious as well as practical significance. As a symbol of the appointment, she would undergo the abhisheka ceremony, usually along with the king’s coronation; she had the right to accompany the king when he performed the rituals. This was especially so at yajnas. Especially in the Ashwamedha Yajna, she had several duties to perform. Of course she would be the recipient of all the merits accruing from those rites. Many myths describe how the mahishi was bestowed with gifts by the yajna deva as a result of the successful performance of a yajna.
On the practical level, she was the second in command in all matters related to politics; it was mostly her son who would be declared the prince and who would undergo the abhisheka ceremony for the purpose. She had access to the treasury and could govern her own platoons. Naturally, rivalry amongst the other queens rose if the mahishi died prematurely, and that led to many conspiracies and occasional bloodshed. Such rivalries were used by enemies to capture power.