Divine Sense

As an action, you can open your awareness to
detect evil forces. Until the end of your next
turn, you know the location of any celestial,
fiend, or undead within 60 ft. of you that is not
behind total cover. You know the type of any
being whose presence you sense, but not its
identity. Within the same radius, you also detect
the presence of any place or object that has been consecrated or desecrated.
See PHB, pg. 84.