Due to the Irradia's unique relationship with an irradiated landscape and in combination with a unique set of genes, some Irradia develope strange powers as a result of their fundemental DNA makeup mutating. While technically a cancer this mutation does not pose any threat to the host, but may, depending on its strength and appearance cause problems in a civilized society.
Your unique genetics have created some sort of supernatural transformation in you. Whether visible or obvious to the average person is up to you and your DM. When you take this feature your Dexterity and Intelligence scores can no longer be reduced past 13. If they are currently lower raise them to that level.
Additionally, you may choose one of the following categories to gain proficiency in; light armor, medium armor, shields, archaic simple weapons, archaic martial weapons, or alchemist’s supplies
As the mutation takes hold the Irradia is first striken with an immense sickness and then a feeling of superhuman power. Your size category, weight, height, apperance, Natural Armor, Natural Attacks, and damage resistances may all be altered. Work with your DM to determine what cosmetic and mechanical bonuses your character gains from this transformation. You also gain the equivalent of one Ability Score Improvement.
As your body becomes infused with radioactive material new senses and control come to you. You may now sense the amount of radioactivity in your area almost like sensing how hot or cold a room is. Additionally, you gain resistance to all necrotic damage.
Your new found connection to the decaying fragments of the universe has begun to grant new powers. Beyond your physical changes you have begun to manipulate the radioactive energy of other creatures. Each creature has their own resistance to this, and older (closer to death) creatures will have some weakness to this ability as they contain far more radioactivity than they did in their younger years.
Some Irradia abilities will require you to use a Nucleocraft dice or request a saving throw against your save DC. Here is how these are calulated;
You learn to invoke a rite of Nucleocraft that infuses your weapon strikes with elemental energy. As a bonus action, you can activate any rite you know on one weapon you’re holding. The effect of the rite lasts until you finish a short or long rest. When you activate a rite, you take damage equal to one roll of your Nucleocraft die. This damage can’t be reduced in any way.
While the rite is in effect, attacks you make with this weapon are magical, and deal extra damage equal to your Nucleocraft die of the type determined by the chosen rite. A weapon can hold only one active rite at a time. Other creatures can’t gain the benefit of your rite.
You choose one rite from the rites below when you first gain this feature. You learn an additional rite each time you gain another Irradia feature.