Detect Undead

For the duration of the spell, you sense the presence of undead within 30 feet of you. If you sense any undead in this way you can use your action to create a faint aura around one undead creature making them visible even if they would not otherwise be so.

The spell can penetrate most barriers, but it is blocked by 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt.