A long time ago, an expedition group from Demacia went to the Shadow Isles to get more information about the devastation the Rune War brought to that place in an ancient time. Some valiant soldiers went together for further protection. Galross was one of those soldiers, even the strongest and the most honored of them. He and the group got fully terrorized with what they saw. That horrid scenery couldn't be better described by that group than a "physical manifestation of the terror as itself".
At the third day in that hellish forest, one of the scientists disappeared. Galros and two other soldiers went after the lost scientist, asking for the rest of the group to reunite later in an agreed place. Unfortunately it got even worse. Galross got lost from the other two soldiers. For those two soldiers, the destiny was merciful to them. They could reunite with the group later, but sadly they had to end the expedition to prevent further losses. So the poor Galross was left behind and suffered alone the "best" welcome the Shadow Isles could offer to him.
Few days had passed. The terror and the darkest essence of that place took over his whole mind and body, changing him slowly. The anger for those he considered his friends and for that homeland he used to love was growing like weed inside his heart. His body didn't resist for too long and he fell into the jaws of the death. Fortunately his soul could be released from that very tortured corpse and finaly rest in peace. However the hatred that grew inside his heart was so intense that it couldn't cease to exist or even leave from that body. The result was the very powerfull and tireless warlike undead the valoran people call Argos. This creature has only one purpose for his existence: Kill every single demacian soul.
"If you find yourself incorruptible, you would easily be surprised by what some places are capable to do with the most honored men." Jarvan IV