The Lost Legion is a group that lives almost exclusively in the Cursed Desert. They are, like the Iotegian, perpetually traveling to avoid the curse of the desert.This nomadic existence makes it hard to combat them.
A group of Xoreth soldiers did not agree with Mirax as new Warchief of the Xoreth, since he surrendered in the war against the Iotegians. They got orders from Meridek before he died to keep fighting no matter what happens, because otherwise the war is not the only thing that will be lost. When king Serbio accused Mirax to still have the group of soldiers under his command, Mirax decided to go in war with the now called "Lost Legion". In the war against the Xoreth the Lost Legion lost one third of their men due death or surrender until the Xoreth had to withdraw their troops. According to many military tacticians the lost legion survived with low supplies of food, water and weapons due to them being trained to fight in arid areas as the vegetation near the Iotegian border was immolated near the beginning of the second great war.
Nowadays the Lost Legion has many more men from different origins like the tribes and the Marauders. They will accept every single person to join the Lost Legion if they will swear they will will fight against the Iotegians until death. If you join the Lost Legion you will get a new name that refers to one of your previous great deeds or profession, this is done so the family of Lost Legion members will not get trouble because of them joining the Lost Legion.