Medallion of Thoughts

The medallion has 3 charges. While wearing it you can use an action and expend 1 charge to cast the Detect Thoughts spell (Save DC13) from it.
The medallion regains 1d3 expended charges daily at dawn. If last charged is used roll d20. On a 1 or 2 the medallion bursts and deals 4d6 Psychic damage to wearer and 2d6 to all within 5 feet of wearer.