Radsoul

The sickening glow of the stars. The horrific burns inflicted by an unknown force. You have somehow awakened and harnessed this force inside, transforming your body into a nuclear engine, and now the movements of the atom stir your own magic. As a radsoul sorcerer, you harness the power of nuclear energy, and the deadly poison of radiation. 

Radiation

1st-level Radsoul feature

Your magical essence is empowered by the various types of radiation. You may activate this innate radiation as a free action, affecting every spell you cast until the start of your next turn. You may do so a number of times equal to your proficency bonus per long rest.

Alpha Radiation. You may add half your constitution modifier (rounded down) as bonus radiant damage with your spell attacks.

Beta Radiation. You may add half your constitution modifier (rounded down) as a bonus to the save DC of one spell that you cast.

Gamma Radiation. You may add half your constitution modifier (rounded down) as a bonus to hit with your spell attacks.

At 10th level, you may add your full constitution modifier instead of half.

Odd Palate

1st-level Radsoul feature

Your body is a perfect refinery for food and drink, allowing you to process just about anything and turn it into energy. You only need to consume half the ration and half the water you would need normally. Additionally, you may eat non-magical materials, and with a successful constitution saving throw turning it into nutrition, enough to count as a ration. The DC for the saving throw is decided by your DM.

Magical Isotopes

6th-level Radsoul feature

You may turn your very magical energy into isotopes that react with the weave itself. After a long rest, choose a number of spells equal to your constitution modifier (minimum of 1) that you know. These spells become isotopes.

Spells that are isotopes deal radiant damage, and if they grant a bonus to your or allies, such as the shield spell, then that bonus increases by 1.

Additionally, you may induce a reaction with an isotope spell. After casting a isotope spell, you may then cast a reactive spell as a bonus action. The reactive spell must be from the same school of magic as the isotope spell that you know. The reactive spell is cast from the original target of the isotope spell. The reactive spell must be of 1st level or lower. You may  do this twice per long rest.

At 12th level, the reactive spell may be 2nd level, and at 18th level, the reactive spell may be third level.

Atom Power

14th-level Radsoul feature

You may cause your magical energy to become incredibly focused, or bursting at the seams. Whenever you cast a spell that has an area of effect, such as fireball you may cause it to either become a fission, or fusion spell. You may do this once per long rest.

Fission. You reduce the effect to increase the area of devastation. For every damage dice you reduce, the area of effect increases by 5 feet. For example, a 3rd level fission fireball may deal 6d6 fire damage, and effect a 30-foot radius sphere. The spell must deal half it's normal damage at minimum.

Fusion. You increase the effect by focusing it into one single point. For each 5-feet you reduce the radius of the spell, the damage dice count increases by 1. For example, a 3rd level fusion fireball may deal 10d6 fire damage, and effect a 10-foot radius sphere. The spell must target a 5-foot size area at minimum.

At 20th level, you may use this feature twice per long rest.

Atom Bomb

18th-level Radsoul feature

Your very essence becomes infused with nuclear power, the unadulterated power of the atom. Whenever you fall to 0 hit points for the first time per long rest, you release a small nuclear explosion, dealing 6d12 radiant damage to every creature within a 30-foot radius sphere, and regaining 10 hit points. Additionally, you exude a 20-foot radius aura that functions like the spell sickening radiance, for 1 minute. If you fall to 0 hit points again, you fall unconscious and the aura dissipates. While the aura is active, you regain 2d8 hit points at the start of your turn.