The physical stamina of your character. If it drops to 0 or below, your character will fall unconcious and will simply lay flat on the ground until the fatigue meter reaches a positive value. Fatigue is important for Mages since Spells drain Fatigue when used. A solid Constitution helps replenishing Fatigue at a quicker rate.
May be increased by spending Character Points on Constitution (+2 FT for each point of Constitution), Willpower (+1 FT for every point of Willpower) or the FT Pool (+4 FT for each point). Gaining a new Level will also increase your FT by 2.