Leoric was once a mighty lord and a devout worshiper of the Zakarum religion. When Leoric decided to start a kingdom he moved to Khanduras and set roots in the town of Tristram. There he set his court in the abandoned Horadrim monastery. Even though Leoric was a foreigner the people grew to respect him. Leoric was a man pure of heart and deeds. It wasn't until the ambassador of the Zakarum church arrived with a letter telling of his great deeds did things go wrong for the once noble king. The ambassador was Archbishop Lazarus, and the letter said Lazarus was the Custodian of Mephisto's Soulstone in Kurast. If Leoric had only known what was going on in Kurast he would have slain Lazarus. Lazarus was, in truth, sent by Mephisto to assist his younger brother Diablo in acquiring a mortal host so that Diablo could walk free. Not long after Lazarus' arrival, Leoric's mind started to decay. Fed lies and visions from Lazarus and Diablo, Leoric declared war on the much stronger kingdom of Westmarch. Leoric sent his most trusted Royal Guard Lachdanan to lead the ill-fated attack. While Lachdanan was away, Diablo and Lazarus tried their best to posses Leoric, but he proved too strong for the weakened Diablo. Diablo then decided to possess Leoric's son, Prince Albrecht. Lazarus led Albrecht underneath the monasteries catacombs to Diablo, where the young prince was no match for Diablo. Driven mad by the loss of his son, he had many innocent people executed for kidnapping the prince. When Lachdanan returned from the quickly lost war he was also accused of kidnapping his son and Leoric ordered Lachdanan to be executed as well. Lachdanan slew the mad king with his sword only to be cursed to eternal damnation by Leoric in his dying breath.
Leoric rose from the dead as king again, only this time it was to be king of the skeletons. He now resides in the tombs under the monastery.