Ruinous Shard

This jagged shard of dark crystal pulses with chaotic energy. While attuned to the Ruinous Shard, you have advantage on checks and saving throws against being frightened. Additionally, once per long rest, you can unleash a wave of chaotic energy in a 30-foot radius. Each creature in that area must make a DC 15 Dexterity saving throw, taking 5d6 chaotic damage on a failed save, or half as much on a successful one. The damage type is determined by rolling a d4: 1 (fire), 2 (lightning), 3 (cold), or 4 (force). Finally, when you deal damage to a creature with this item, you can choose to gain temporary hit points equal to the damage dealt, up to a maximum of 10 hit points.