In this episode, we talk about how to take a concept from a standard monster and change it fundamentally to create a new monster. How can you take a siren from Greek mythology and change it to use fear to lure their victims toward them? Then apply this to other monsters in your game. This helps as well if you have a meta gamer (or two) in your group.
You can also do this to your entire game world as well. Is this part of the world slowly poisoning your gaming group? Will they only figure it out as they start to fail saves as you call for random rolls every morning of game time?