As a reaction, which you use when you are reduced to 0 health, you can instead burst with radiant energy. You instead drop to 1 health and regain 3d6 health. Each creature of your choice in a sphere around you must make a Fortitude saving throw.
On a failed save, a creature takes 4d6 radiant damage.
On a successful save, a creature takes half as much damage.
You can increase the healing by 1d6 and the damage by 1d6 for each additional mana or psi expended.