This spell allows the caster to detect sources of heat with his eyes. These sources may range from ambient temperature to the heat of a powerful fire. Any such source of heat possesses an aura with a myriad of colors ranging from red to white, called a heat signature. Accordingly, the caster gains a competence bonus to Spot checks involving such sources corresponding to the severity of the heat signature's color. The most 'severe' color is always closest to the source of the heat signature, and may be surrounded with less severe colors as the heat diminishes the further it gets from the source.