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 2d6 + your spellcasting ability health. Each creature other than you in a sphere centered on you must make a Fortitude saving throw.

On a failure, it takes 3d6 radiant damage.

On a critical failure, it takes twice as much damage.

On a success, it takes half as much damage.

On a critical success, it takes no damage.

Augment

You can increase the healing by 1d6 and the damage by 1d6 for each additional mana expended.