After a session

If someone introduced an element (NPC, monster, situation, etc.) during a session, and it might cause trouble later, write it up as a threat while it's still fresh in your mind. Or at least make note of it, and write it up in full later. This will serve as a reminder to bring it up in future sessions.

After their first adventure, the PCs returned to explore the ancient tomb and Blodwen disturbed the spirit of the mummified Green Lord interred within. While it mostly keeps to its blissful, constructed afterlife, it could definitely cause trouble for the PCs later.

I write it up as a threat (a magical entity*).*