 Dost was tasked with protecting the dowager Rani (queen) and her estate.When the Rajput neighbours of Mangalgarh, led by the Thakur of Parason (now a village in Berasia tehsil), formed an alliance to counter the growing power of the Rani of Mangalgarh, Dost Mohammad Khan defeated them.During his service at Mangalgarh, Dost married a Rajput girl from the Mangalgarh royal family, who later converted to Islam and adopted the name Fatah Bibi (also spelled Fateh Bibi).