“ 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...”
“ Inside a mad scientists laboratory the PCs find a short creature with smooth, oily and whale like skin. The head is faceless and smooth also. But hundreds of white eyes on the PCs from the fat belly of this creature. The PCs are about to kill it as it speaks to them in a feeble but intelligent voice, asking them to pour the contents of a green vial on it. Will they do so? And if so, what will happen?”
“ While it is within your purview to write long-spanning histories of your world, it is largely unnecessary. If you are running an RPG, do this instead: make a bullet point list of important events that affect the world today, and mysteries that people still don't know. Let these fuel your adventures.”