I use a lot of sources of information when coming up with game ideas. Reality generally provides some of the best stuff, to be honest. I found a book on bizarre, real crimes over the ages that was great fodder. Today, I found an interesting article about
a fungus that takes over ants. I've used other ideas from real life, such as
a giant fungus - which of course in game a necromancer messed with and turned undead - and
a wasp with larva that take over its host spider.
The world is a great place - we just have to look around to see it.