Muhammad Ahmad: "the Mahdi", Death toll: Probably hundreds of thousands. The title "Mahdi" in Islam is similar to that of "Messiah" in Christianity or Judaism: the Mahdi is a prophesied chosen one who will rid the world of evil, and rule the world (by Islamic law) for several years before the Day of Judgment. Throughout history, there were several Islamic cults whose leader claimed to be the Mahdi or to be making way for the appearance of the Mahdi (this includes modern-day ISIS). But probably history's bloodiest Mahdi was Muhammad Ahmad. Ahmad was a 19th century claimant to that title, who rose up against the Egyptian/Ottoman authorities that ruled the Sudan at that time, and later waged war against the British interests in the region. He quickly amassed an army of 40000 faithful, originally armed only with primitive weapons, who rapidly defeated incompetent Egyptian troops and took possession of a large cache of modern guns. He went on to defeat Ottoman forces under the command of British soldiers-of-fortune. He then went up against British-controlled Sudan, where the famed General Gordon held up resistance as the Mahdi besieged Khartoum for a year. By the time the British army sent a relief force, it was too late, they arrived only days after the city had been taken and Gordon had been killed. The Mahdi's armies kept sweeping across Sudan, taking almost all the British territory. The Mahdi's military victories, backed up by Islamic prophecies and the support of various different Islamic religious leaders in the region, made him rise to enormous fame and prestige. Originally, the British had been reluctant to engage in full-scale war, but the heroic death of Gordon (who in the year of the siege had become a household name and popular hero to the British public) left the government no choice but to launch a major expedition to stop the "Mad Mahdi and his Dervishes". Ahmad had set up a regime in his territory based on Sharia law, but with the addendum that all Muslims in his lands had to swear allegiance to him as Mahdi, and acknowledge him (and not Islamic tradition) as the supreme judge of Islamic law. Anyone, Muslim or not, who defied his authority was put to death. But just six months after the capture of Khartoum, the Mahdi died of typhus, which was not very good for his image, given that the Islamic prophecies kind of depended on the Mahdi not dying. Even so, it took another 14 years for the British to decisively defeat the Mahdist forces, after which they destroyed his tomb and threw his bones into the Nile river (except for his skull, which was kept as a prize by the victorious British General Kitchener).