The atom is the building block of the universe. Locked inside is a limitless font of power, waiting to be unleashed. Many who have bathed in the deadly embrace of radiation have crumbled, but some select few of the survivors may find themselves irrevocably altered. A sorcerer tainted by radiation can become a nuclear powerhouse, so long as they can avoid melting down.

Radioactive

At 1st level, your inner glow grants you an internal powerhouse from which to draw magic. You gain resistance to radiant damage, advantage on saving throws against being irradiated, and you learn the Light cantrip if you don’t already know it.

Additionally, you learn an additional spell when you reach certain levels in this class, as shown in the Nuclear Spells table. The spell counts as a sorcerer spell for you, but it doesn’t count against the number of sorcerer spells you know.

Nuclear Spells

Reactor

Starting at 1st level, you can harness your atomic energy to expand your magical influence. When you cast a sorcerer spell that creates an effect in a cone, sphere, or cube, you can choose to increase the size of the effect by 5 feet. For example, if you cast Fireball, which affects a 20-foot-radius sphere, you can increase it to a 25-foot-radius sphere.

At 14th level, you can increase the size of the effect by 10 feet.

Fallout

At 6th level, your magic carries traces of withering radiation. Once per turn, when you cast a spell of 1st level or higher on your turn, you can cause one creature targeted by the spell to make a Constitution saving throw against your spell save DC. On a failed save, the target suffers one level of Irradiated, to a maximum of level 3.

Additionally, when you cast a spell that deals damage, you can spend 1 sorcery point to change the damage type to fire or radiant.

Quantum Jump

At 14th level, as a bonus action, you can magically teleport up to 60 feet to an unoccupied space you can see. Immediately after you disappear, a wave of radiation spreads within a 10-foot-radius sphere centered on the space you left. The radiation remains for 1 minute. When a creature moves into the area or starts its turn there, that creature must make a Constitution saving throw against your spell save DC, taking 2d10 radiant damage on a failed save, or half as much damage on a successful one.

You can use this feature a number of times equal to your Charisma modifier (minimum of once). You regain all expended uses after a long rest.

Unstable Fission

At 18th level, you can split your atoms into an unstable twin of yourself. You can cast Simulacrum with a casting time of 1 action, a range of self, and without requiring components. A simulacrum created this way cannot cast cantrips and cannot use spell slots higher than 3rd level.

When the simulacrum is reduced to 0 hit points or after 1 minute, it explodes. Targets within 30 feet of it must succeed on a Dexterity saving throw against your spell save DC. A target takes 3d10 thunder damage and 3d10 radiant damage on a failed save, or half as much on a successful one.

Once you use this feature, you must finish a long rest before you can use it again.