I love the concept of Digamma Radiation as it stands now - some strange, esoteric, possibly malevolent force of nature from beyond the stars that wrecks havoc on the body and mind with no easy way to detect or mitigate it. However, I think its not utilized as much as it could be, and could really benefit by leaning more heavily into the whole eldritch / cosmic-horror-esque thing its got going on.

These are, of course, generalized suggestions with no grounding in how the development process is actually being handled. There is no obligation to take these ideas, but brainstorming is fun and can possibly lead to fun additions that at least touch the concepts later down the line. Without any further ado, some ideas for Digamma-related stuff:

Mad Creatures

Its somewhat-established that Digamma Radiation has some sort of effect on the mind, what with the whispers and ghostly apparitions and all. Perhaps this could be used to greater effect if it acted upon mobs more as well - specifically, driving creatures stark raving mad. Instead of just decreasing their health, non-player entities could become extraordinarily violent and persistent in attacking anything and everything around them as they slowly succumb to having their brain melted.

Hallucinations

Digamma already has a few smaller hallucinations, the shadow men and the growing presence of the Crimson Star being the two most obvious. However, more is usually better and these two alone are rather tame. Phantom armies of geared up super-mobs that drain your hunger or stamina instead of health? Being dragged down into the floor by shadowy hands and knocked unconscious for a stint as the whispers of malevolent entities beyond mortal ken sandblast your brain? The possibilities are nearly limitless.

Reality Warping

This one is a bit more lofty than the others, but I feel like Digamma could be made a true and proper threat on par with actual radiation.

What if there was something more to Digamma? Some great and powerful reward for delving deeper into its power; items, technology, weaponry and more to uncover... at a price. Experimentation with Digamma could have a range of consequences such as those discussed above, but also more - warping the nature of reality itself, imbuing itself into the environment. Something akin to a Black Mesa scenario; an experiment needed to progress that if not done correctly could open a gateway to the Digamma system itself or something similar and letting truly unfathomable amounts of the stuff rush in from every side. Crimson storms and portals that release entities of pure Digamma while warping the environment and creatures around themselves into crude mockeries of life.

If not stopped, Digamma Storms could perhaps herald the end of your world - spreading out more and more and more, becoming stronger and more uncontrollable until the entire surface is reduced to something utterly alien and completely hostile.

And other stuff

(That I'll put here later if I think about them)

Honestly, I always thought of Digamma Radiation as something on par with the Psy Fields from STALKER... Some kind of energy which gets into the brain and can control you if you have a strong mind, or psychically lobotomize you and turn you into a zombie if you're weak-minded. I love the idea of the reality-warping, hallucinations, and insane creatures... If I had any kind of programming skill I'd make a multiblock psychic emitter structure similar to the Brain Scorcher or Miracle Machine from STALKER Shadow of Chernobyl... A giant antenna that emanates psychic energy to fry the brains or mind controls everything within an extremely large radius, with only certain kinds of specialized armor protecting you from the psychic energy. Also perhaps something akin to the Monolith which can at random cause psychic pulses that kill everything within a large radius if they're not protected behind a decently robust form of cover, like an underground bunker of some kind.