Information is the key to battle. A good warrior, whether fighter or mage, must train to remain aware of the movements of enemies. Honing one's senses will allow a combatant to detect others entering and leaving the area.
Every time another player enters or exits the room you are in, your Awareness skill will attempt to notify you that the player has entered or exited. You can tell where players are going to (You sense Player leaving for The Main Gate of Tos.) but not where they are coming from (You sense Player entering the area.) Awareness messages will be bold for enemies that enter and exit. (You sense Player entering the area!) Anonymous, morphed, and invisible players if you have no detect invis will all simply show up as 'someone' when entering or leaving. Based on Intellect, which is important for beating the counter-skill 'Sneak' (see level three).
All characters start with this skill.