Nuclear Sorcery

"So wait, you fell into a mine and... what happened?"
"I found that glowing green rock. It looked crunchy so-"
"So you ate it?"
"So I ate it."
"And now you can use magic and explode?"
"Yeah, pretty much. Pretty nifty, eh?"
"Dude, what is wrong with you?"
"I was hungry.."
"Whatever. How do you plan on telling everyone?"
"In a bar fight."
"Oh no."
"Oh, yes."

Your innate magic comes from the power of nuclear energy. Many with this power can trace their magic back to a near-death experience caused by radiation exposure, but perhaps you were born during a nuclear eldritch storm so powerful that folk still tell stories of it.Whatever the case, the magic of nuclear energy permeates your being.

 

Radioactive

Starting at 1st level, you can release nuclear energy stored within yourself. As a reaction to taking damage, you can create a miniature nuclear explosion. Every creature of your choice within 20 feet of you must succeed a Constitution saving throw against your spell save DC, taking 2d6 necrotic damage on a failed save or half as much on a successful one.

The damage and size of the explosion increases to 30 feet and 3d6 at 6th level, 40 feet and 4d6 at 11th level, and 50 feet and 5d6 at 16th level. You can use this reaction a number of times equal to your Charisma modifier, with uses resetting after a long rest.

Particle Accelerator

Starting at 6th level, you can force nuclear power into the spells you cast. Whenever you cast a spell that does force, radiant, necrotic, or poison damage, you can make the spell do an additional amount of damage of that spell's type equal to half your sorcerer level, rounded up. If a creature takes damage from a spell that has this feature applied to it, they must succeed a Constitution saving throw against your spell save DC or be poisoned for one minute. The poisoned creature can repeat the saving throw at the end of each of their turns, ending the effect on a success.

You can use this feature a number of times equal to your charisma modifier, with uses resetting after a long rest.

Nuclear Body

Starting at 6th level, you can choose to emit a radioactive aura. As an action, you can cause yourself to gain resistance to necrotic and radiant damage, and you emit bright light in a 20-foot radius and dim light for an additional 20 feet. This transformation lasts for one minute and has an additional benefit that you can choose. You can use this feature once per long rest. At 20th level, you can use this feature once per short rest and choose two additional benefits instead of one.

Atomic Fusion

While Nuclear Body is active, you can force two spells to fuse. Choose two spells that you can cast with a casting time of one action and require a roll to hit. As an action, you can cause the effect of both spells to occur simultaneously, The combined spell has range of 30 feet and requires one spell attack roll. It does the damage and causes the effects of both spells. You can combine spells like this 3 times per Nuclear Body.

Exponential Fission

While Nuclear Body is active, the next damaging spell you cast that hits a creature does 1 additional necrotic damage. The second spell that hits a creature does an additional 2 necrotic damage. The third spell that hits does an additional 4 damage. The fourth does an additional 8 damage, the fifth does an additional 16, and the sixth does an additional 32 necrotic damage. This exponential extra damage resets on the seventh successful spell hit. 

Radioactive Melt

While Nuclear Body is active, you radiate damaging, searing energy. Whenever a creature enter within 20 feet of you, they must make a Constitution saving throw against your spell save DC or take 3d10 fire damage. Flammable items that aren't being worn or carried combust when within 20 feet of you. This heat is enough to cause wood to char and some metal to fuse and start melting.

Extended Half-life

Starting at 14th level, your body becomes extremely unstable whenever you are near death. Whenever you are at 0 hit points and aren't stabilized, you gain the following effects:

• You shed bright light for 40 feet and dim light for an additional 40 feet.
• You are aware of your surroundings despite being unconscious
• You trigger your Radioactive trait at no cost every time you make a death saving throw .
• You die when you reach 5 death saving throw failures instead of 3.

This feature activates no more than one time per long rest.

Atom Bomb

At 18th level, you can create a nuclear explosion capable of leveling cities. As an action, you can expend 15 sorcery points and a ninth level spell slot to explode with violent force. All creatures within one mile of you must make a Constitution saving throw, taking 11d10 thunder damage and are pushed 60 feet away from you. If they are within 1,000 feet of you, they take an additional 11d20 force damage. If they succeed the save, the damage and push distance is halved. 

This explosion creates a massive mushroom cloud that can be seen from ten miles away and heard from five miles away. The explosion does ten times as much damage to objects and structures. The one-mile area of this effect is filled with deadly nuclear energy for 2d4 x 10 years. No plant life can grow there for that time, magical or not- and any creature that spends more than one hour in the zone must make a DC 20 Constitution saving throw every hour or suffer one level of exhaustion. 

Using this ability reduces you to one hit point, and you cannot use it again after you finish 10d4 short or long rests.