Ivory Cup

A cup of ivory, carved with a simplistic motif of angels and small enough to fit in the palm of a hand. While holding the cup, you have resistance to lightning damage. This item has 1d10 charges. As a reaction when a Cleric or Paladin casts a spell within 120 feet of you, you may expend one of the cup’s charges. When you do so, you regain a number of hit points equal to 1d4 times the level of the spell slot expended. After doing so, the cup tingles with energy and faint arcs of electricity crawl across its surface, though this does not harm you in any way. The cup regains 1d10-1 expended charges daily at dawn. When the last charge of the cup is expended, roll 1d20. On a roll of 1, the cup explodes, sending shards flying with a small burst of electricity.