[7] He has been described as belonging to the Karnat Kshatriya Kula and began to rule Mithila from the citadel of Simraungadh which was situated on the modern India-Nepal border, in 1097 CE.

The Chalukyas would likely have been accompanied by many military adventurers who carved out small principalities of their own in Northern India and Nanyadeva would have been among them in capturing land in the Mithila region of North Bihar.

[12] Inscriptions from the Sena dynasty of neighbouring Bengal refer to Nanyadeva as "Karnata-Kulabhusana" indicating an origin from the area around modern-day Karnataka in India.

Nanyadeva was a contemporary of Ramapala of the Pala Empire with whom he had fallen into conflict and then subsequently gained independence for Mithila.

[12] Following on from the Varendra rebellion, the Pala Empire was in a state of disintegration with the Sena dynasty establishing a power base in the Radha region.

[12] To compensate for these losses, Nepalese traditions assert that Nanyadeva launched attacks into the Kathmandu Valley of Nepal which at the time was under the Thakuri dynasty.

The Karnats mainly split into two branches with Nanyadeva's descendant, Harisimhadeva fleeing to Nepal and marrying into the reigning Malla dynasty.