“ The PCs discover a large white ball in the branches of a tree, or in a niche in a cave. Unless magically examined, or by a PC with a specialty in insects, it is a plain, smooth white ball. After a short time, it hatches and releases hundreds of spiders, cockroaches, some other nasty bug”
“ Many games draw moral lines in bold colors, where the real world is not so easy to categorize. Suppose that the player characters are faced with an overwhelming foe? Even unsavory allies such as orcish barbarians may be better than no allies at all. More disturbing, these allies may be honestly friendly to the PCs when all is done, overcoming barriers of race and religion. Will the PCs remain friendly with the bloodthirsty humanoid tribesmen when their mutual foes are defeated? Some would expect the tribes to betray them, but after the characters have honestly won their respect, even orcs may not be all bad.”
“ Pick up a pathology/microbiology book, and add the diseases/syndroms to your game. Your players will freak out.
Coughed at? Diphteria. or tuberculosis?
Drunk from a muddy stream? Or just walked through? Well, let us introduce you to schistosomiasis...
Hit by a stream of energy? Too moch mana is ust like too much radioactivity - perhaps all mages could develop cancer early if too powerful...”