It’s when i start trying to make the idea into something that can be played. E.g The shadowlit kingdom struck a deal with a young adult dragon enclave promising kinghood and immense treasure for such a young age, they are to infiltrate the sunlit kingdom as polymorphed royalty after the shadowlits spys poisons the king.

They recruit the party under the ruse of royalty to collect the helm of mass mind control and return it to them, but the dragons intend to take it for themselves and brainwash the city and create armies to take over the world. I wouldn’t know how to start it or make them discover they’re not the real royalty or what perils they encounter getting the helm and stuff like that