In a campaign I ran, I had the party wake up in the bilge of a ship, tied up after being drugged. They all had a fresh, moonshaped tattoo in their neck.

I planned to have some guards talk with eachother nearby, giving them some exposition how they got there, and then the ship would bring them to a harbour where they’d be unloaded and brought into a colosseum where they would become gladiators and the rest of the story would happen there.

Instead they used magic and lockpicking to get rid of their chains and killed the guards before they could say anything. The orc of the group then proceded to punch a hole into the outside wall of the ship, causing all the remaining guards to abandon the ship on the lifeboats. They then managed to beach the ship on the nearby shore.

As a “punishment” I kept dangling the importance of these tattoos over them all the time, without ever telling them what they mean.