The gem stores necrotic energy within it. While attuned to it, you gain resistance to necrotic damage, half of the damage taken by you, and half the damage stored as energy within the gem. When the gem has stored at least 60 damage worth of necrotic energy, the stone is now primed for use. You can use an action of your turn to release an explosion of necrotic energy. Each creature within a 10 ft radius must make a DC 15 dexterity saving throw or take 6d8 necrotic damage, or take half that on a failed save. You regain hit points equal to half of the total damage done to creatures around you.

Notes: Resistance: Necrotic, Utility, Warding