Hunters have the ability to place traps when out of combat. When cast they will appear on the ground at the hunter's feet, where they will remain for a time unless triggered. If an opponent steps on a trap it will go off, inflicting its effects on the target. Traps are not triggered by friendly targets so you need not worry about your pet or your party members accidentally stepping on them. You can only have a single trap active at any one time. Traps are generally invisible to your foes, but there are skills and abilities that can allow them to perceive them.