Minohtar was King Ondoher's siter-son. One of the captains who went to war with King of Gondor, in the final fateful engagement with the Wainriders. He was the commander of Ondoher's right wing when the chariots of the Wainriders launched a surprise assault, an attack that left both Ondoher and his heir Artamir dead. Minohtar took command of the army, and ordered a strategic retreat.
While Adrahil I of Dol Amroth led his section of the army southwards into Ithilien, Minohtar commanded a hopeless rearguard action in the country south of the Dagorlad. Valiantly though he fought, his force could not stand against the Wainriders, and he himself died of an arrow wound.
Imagining that Gondor had been defeated, the Wainriders carelessly celebrated their victory with a feast, little suspecting that the Gondorian general Eärnil was advancing from the south. His Southern Army fell on the Wainriders and overwhelmed them, ending their threat against Gondor.
These battles saw the loss of King Ondoher and both his sons, bringing his line to an end. Minohtar was ready to send a message to Faramir son of Ondoher to notify him that he was now the King, only to be told by the leader of the Éothéod that he had just died disguised as a soldier.
The Wainriders poured relentlessly into Ithilien until late on the thirteenth day of Cermië Minohtar was overwhelmed and slain by an arrow. His men carried him out of the fray, and all that remained of the rearguard fled southwards to find Adrahil.
The chief commander of the Wainriders called a halt to the advance, and held a feast only to find their death from Eärnil II in the Battle of the Camp. Minohtar would very likely have succeeded his uncle as King of Gondor. As it was, no close kin of Ondoher survived the war, and the Crown eventually went to the victorious general Eärnil.