Vital statistics are unlike skills and stats. They get used up as your character performs actions or as certain situations affect your character. You can check on your vital statistics by typing
health in the game.
Essence represents how much magical energy your character can manipulate. As your character casts spells or uses magical items, your essence will deplete.
Stamina represents how much energy your character has for physical actions such as running and combat. As your character performs difficult or physically draining moves, your stamina decreases. If your stamina decreases to 0 you will fall down exhausted.
Vitality represents the amount of blood you have. Taking damage will almost always cause a loss of vitality, as will bleeding. Your character will die if their vitality reaches 0, so it is best to use certain healing herbs or methods to replace lost vitality.
Willpower represents how much drive to keep acting your character has. You character will spend willpower to activate abilities by force of will alone. Your character will fall unconscious if its willpower reaches 0.