When attuned to this item, you will feel a strange necrotic power seep into your own pool of arcane ability.

For your proficiency bonus times a day, when casting a cantrip, you can choose to change the damage type from whatever it was already doing to Necrotic damage. The damage dice of the cantrip remains the same. 

This ability recharges after a long rest. 

Notes: Arcane Focus, Focus