Will the Mahdi appear at the end of time? Did Al-Daraqutni or Ibn Al-Qayyim deny his emergence? Is belief in him obligatory?

One must believe in the advent of the Mahdi at the end of time, and that he will fill the earth with justice and fairness, just as it was filled with oppression and tyranny; this is due to the continuous transmission (mutawatir) of prophetic traditions regarding it. There is no consideration for any dissenting opinion after its establishment from the Prophet, peace and blessings be upon him.