Soul fueled blood

Fueled by the exsisitance of your two extreme souls, your body has become more attuned to their presence. You gain and receive the benefits of a third type of blood cells within your body.

Depending on what soul fuels your body, you gain the following benefits.

Fueled by your black soul, your black cells give you necrotic immunity. When hit with melee attacks within 10 feet, you deal 2d4 acid damage to the attacking creature.
As your white soul fuels your body, your white cells give you immunity to radiant damage, you begin to regenerates 5 hit point per turn, even regenerating a limb after a long rest.

Black/white Purge (5/6 recharge or half)- 20ft nova attack, each creature within range makes a con save, on success half damage, on failure  2d10 acid/radiant depending on which soul is active and Blinding effect.