Endurance represents how worn down you are by constant activity. It goes up naturally, and goes down as you move or perform other physical actions. When you run out of endurance, you'll be unable to perform many taxing physical actions. The rate at which your endurance recovers is determined by race and the level of your mini-skill called Fitness. This rate is increased slightly when you sleep. Other ways of recovering your endurance can be attributed to various class skills and Ankyrean artifacts.