Lethan, a former resident of Stratholme, was previously known as Martinius. Educated in Dalaran and proud human of the Alliance. When the scourge reached Brill, he went west to see if he could help, but was forced east by the increasing number of scourge minions, and ended back to where he started off, Stratholme. When the plague reached Stratholme, he was infested and turned undead, however he was one of the survivers of the culling. Many of Martinius friends and family was killed.
After a while, he broke free from the scourge, and declared himself Forsaken. He could not remember his human name, and called himself Lethan. After going to Stratholme, he found some old book entries, one of them mentioning him and his name "Martinius". Lethan decided then to add Martinius after his name, but Lethan is still the name he is called by his fellow Forsaken.
Many of Lethan's friends and fellow mages turned to the dark side and became warlocks after they turned Forsaken, but Lethan still holds on to the arcane arts, of which only a pure mage can perform.
Lethan is a Community MVP on the official World of Warcraft forums.