Rare Wondrous Item (Crown), Requires Attunement

Peace in Death. When a creature within 30 feet of you regains hit points, you can use your reaction to choose an Undead within 30 feet of the creature and pacify them with the flow of healing and calming energy. The undead must make a DC 14 Wisdom saving throw, taking radiant damage equal to the amount of Hit Points regained by the creature on a failure, but only to a maximum of 50. 

Fatal Sight. Once per short rest, you can use your bonus action to choose a creature that you can see. You can choose to learn one of the following information about the creature: condition immunities, damage immunities, resistances, vulnerabilities.
You can also instead use this feature to spend 1 minute examining a corpse that died within the last 24 hours. You automatically know their last words and how they died.   

Gravekeeper’s Sense. Twice per long rest, you can also use your action to sense the type and location of all undead creatures within 120 feet of you for 1 minute.