10. Conquests of Timur, 1369-1405, 15-20 million

Timur, aka Tamerlane, aka Tamburlaine the Great was a Mongolian who sought to restore the glory of the Mongol Empire of Genghis Khan. While he didn’t quite conquer as much as his predecessor, he did a pretty freaking good job. Across Middle East, India, Central Asia, Russia, he conquered and attacked many of the Muslim empires of the region, slaughtering as he went, but retaining keen skills in statecraft and was a patron of the arts. His eventual Timurid Empire stretched from Turkey to India, due in part to his incredible foresight, including planning his campaigns years in advance. His campaigns carried a fierce death toll, some 15-20 million people died in the formation of this empire.