Axel Mortmain, also known as the Magister, was the head of the Pandemonium Club until 1878. Having slowed his aging through the use of dark magic, Mortmain dedicated his life to avenging his parents' deaths. He made Tessa Gray's existence possible, hoping to use her for his own purposes to create a new race, a form of warlocks, half-demons and half-Shadowhunters, that are superior to the Nephilim and meant to cause their destruction.