Shield creates an invisible, mobile disk of force that hovers in front of the character. It negates magic missile attacks directed at the character. The disk also intercepts attacks, providing three-quarters cover (+7 AC and +3 on Reflex saves against attacks that affect an area). The disk moves out of the way when the character attacks, so it does not provide cover to opponents. The disk protects the character only against magic missiles and attacks from one direction. The character designates half the battlefield as being blocked by the shield. The other half is not. The character can change the defensive direction of the shield (that is, rotate the dividing line) once as a free action on each of the character's turns.