This is a Divine Aura
You and friendly creatures within 10 feet of you has resistance to necrotic damage, and its hit point maximum can't be reduced. In addition, a nonhostile, living creature regains 1 hit point when it starts its turn in the aura with 0 hit points.
You can use a bonus action to cause you or any friendly creature within 10 feet of you to regain 1d6 hit points.