Detect Morality

When you cast this spell, choose chaos, evil, good, law or neutrality*.

While this spell lasts, you gain the ability to detect the chosen alignment as if seeing a glowing aura around a creature or item so long as that creature or item is within range. The size and strength of this aura depends on the detected creature's Challenge Rating (i.e. a Prince of Hell would give off a much larger and more powerful aura than a lesser devil) or a detected item's relative power level as determined by the DM. This aura disappears when the spell ends. The area of affect moves as you move. 

The spell can penetrate barriers, but 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt blocks it. Animals, traps, poisons and other potential perils are not evil, and as such this spell does not detect them.

* When detecting neutrality, you must choose an axis (Lawful to Chaotic, Good to Evil).