The magician uses a reflective surface of any size to track creatures in the nearby area.   The reflective surface communicates the number, location, and size of creatures that are between 10" and proficiency bonus x 100" of zim, and can only be seen by the magician.   Only creatures sized medium or larger are detectable, and creatures cannot be detected if they are separated from zim by 1 inch of lead, or if the creatures are undead or constructs.   The information is only updated at the start of each of the magician's turns.