Before Equestria was discovered, Star Swirl the Bearded traveled to many lands to uncover new forms of Magic. On his journey, he crossed paths with a dark sorcerer of equal measure. Grogar the Ram Necromancer. He only desires to reign dominant among all others. His evil intent draw the two to battle each other. But in the end, it was Star Swirl who prevailed. He imprisoned Grogar into the deepest, darkest pit there ever was. While imprisoned, his new-found hatred for Star Swirl and his kind grew, for he fears pony magic will defeat him again, and swore to seek vengeance on all of ponykind. Guarded by Windigos to prevent Grogar's escape, with only his burning hatred keeping him warm. In time, the pits leading out from Grogar's tomb became a prison for all forms of evil creatures. This dark realm became known throughout the ages as "Tartarus".

Inferno (Dante)