For every level of spell there appears an image of the recipient that does exactly as he or she does. There is no way to tell which is the original except by magical detection. On hits to the images roll appropriate die to see which is the real image. Once an image is hit it disappears. Mirror images remain with arm's reach of the recipient.
This spell is only extendable if the caster is the target; but the duration may be increased as normal with additional levels.