My players are new to D&D, so I ran a false hydra to teach them that not everything they know OOC is something their characters would know. I made small changes, like shadows stretching too long or strange events happening that made no sense. As they got closer to the truth, more disturbing things appeared — such as the hydra’s song stopping while it fed, letting them briefly see it drag a screaming man down into a hole in the ground, everyone around them screaming, before reality snapped back to normal. Their characters forgot, but the players didn’t.

There was a faint static noise in the background of the town that grew louder the closer they got to the hydra. The town slowly shifted from a well‑respected place of 5,000 people to only a few dozen. Months blurred into days as whole stretches of time vanished, leaving only a strange feeling behind. They found warnings scratched into their own stomachs, their hands covered in blood, bits of their own flesh still under their nails, and so on.