Agramahishi/Pattarajmahishi was considered the Chief Queen of the Emperor. She gained a salary and had the right to sit next to the King and even participate in the administration as long as the King allowed.
Durdhara was Agramahishi of Chandragupta Maurya.
Dharma is called Agramahishi of Bindusara in Mahavansh Tika but she was a commoner in Ashokavadana.
Asandhimitra was Agramahishi of Ashoka and after her death Tisyarakshita was given the post till she burnt Kunala’s eyes and Ashoka tortured and burned her alive in his torture chamber.
Then there were Devis who were ladies of good and noble lineage and their children had right of inheritance, Darakas were also secondary wives and then there were Bhoganyas who were pleasure women and kept only for physical satisfaction.
Mauryans Empire also had Ganikas (Courtesans) and Dasis (Megasthenes denies this but Arthashastra explicitly mentions slavery system).