If your familiar is within 60 feet of yourself, you can take a Magic action to dissolve its magical bond to this plane. Your familiar drops to 0 Hit Points and unleashes necromantic energy in a 20-foot Emanation. Each creature you choose within the Emanation makes a Dexterity saving throw against your spell save DC. A creature takes 8d10 Necrotic damage on a failed save, or half as much damage on a successful one.
Once you use this feature, you can't use it again until you finish a Short or Long Rest. You can also restore your use of it by expending a level 6+ spell slot (no action required).