One of the other things I don’t like about the Iron God Adventure Path is the extensive use of scientific terms. I do my best to avoid this and rename things more appropriately Nimmerians don’t use the word radiation, for example, as this is a scientific term. Though the locals are well aware of its lethality and refer to the affects as the Phantom Death. For convenience I usually just call it what it is – radiation poisoning – around the gaming table.
Credit to Fallout for the name and the WoTC DM forum members who gave me the idea to use exhaustion (5e) as a mechanic to replace ability drain (3.5e).
Radiation can be naturally or artificially produced. All stars produce radiation in some variety, and planets closer to these stars typically suffer more severe effects than worlds farther away. Many starships and other pieces of technology incorporate radioactive parts and fuel cells that can flood an area with harmful radiation when ruptured or exposed. Ancient alien civilizations might leave behind powerful artifacts that emit harmful radiation. Whether the source of the radiation is natural or artificial, any character in an environment rich with radiation may suffer some negative effects for exposure.
Radiation is a contact poison effect the severity of the exposure determines the lethality of the dose (and the DC). Creatures that are exposed to radiation must make a Constitution saving throw each round or suffer levels of exhaustion, as set out in the Radiation Damage table.
Radiation is poison damage and any ability or spell that affects poison will, likewise, affect radiation damage. Creatures that are immune to poison damage take no damage from radiation, and creatures resistant to poison damage reduce the strength of the effect by one step. For example one level of exhaustion would become poison status effect.