Capability Radiation

[Shazuli]

A Capability added to every single living creatures (undead would be immune). A block or item can either "emit" divided by the distance (return emission/distance) or block with a line of sight (return emission*blocking).

This value automatically goes down by time and can't be sped up or something, the rate this goes down is constant but unchanging. A timer will start if this goes over a certain threshold and keeps track of how long it has been over that level. That timer will give Radiation Sickness after n amount of time and gradually increase the intensity of it. A lethal level will make the value go super high, impossible to have time for it to drop down to a safe level and is, well, "lethal". Protection against it is an obvious thing you can do. Haz-mat Suit is one example for external sources, another is placing Radiation resistance blocks around something. When in your inventory you can't really place blocks to protect you further, but surrounding it in your inventory would add additional protection:

Not sure if some dimensions would give a natural radiation emission to creatures there. Either a negligible amount such as in the Overworld (goes down faster than it increases), but in other dimensions such as Space would gradually make it go up over a long time. Other "magical" dimensions such as The End would probably give 0 radiation emissions.

[Shazuli]

An example visual how it would work with external sources. The bar here shows how much their "exposure" value has risen over the time stamp.