There’s always a bit of a discussion on just how gonzo D&D should be and those “weird” modules that had rayguns in them.
How can you have rayguns in D&D? It doesn’t make sense! Why would there be swords and magic and ALSO rayguns!? It’s just not supported!
Except it totally is.
I’ve been reading an Andrew. J. Offutt novel, Chieftain of Andor [hat tip to Schuyler Hernstrom], which features stone age atomic death rays.
The setting is a Sword & Planet world where there are explicitly no firearms [lack of saltpeter is cited], primitive swords are the weapon of choice for most civilized peoples, and sorcery is real [‘A does not necessarily equal A’]. Yet the hero ends up with an atomic death ray. How?
Two races of mermen live in the caverns underneath a mountain composed in part of a radioactive mineral. The blind albino mermen in the upper part of the mountain have devised a weapon: a small obsidian mirror-box that contains a tiny chunk of highly radioactive material. There’s a door flap that is opened by pulling on a simple trigger. Whatever is in front of the box gets Lou Slotined.
Of course construction of the device is always fatal to whomever harvests the rock and assembles it, so there are necessarily very few and they are only made when absolutely necessary.
The hero observes that in the hands of anyone else on the world other than the blind albino mermen who never leave their mountain, the device could lead to a devastating holocaust, and he’s reluctant to accept the one that is gifted to him for saving the beautiful blind albino mermaids from the chief of the not-blind albino mermen.
So, uh… yeah. If you need some sort of justification for why or how you might have death rays in your AD&D game where swords and wizardry are the words of the day, you need look no further than Appendix N.