In some ways, it was similar to the rules of the Spirit that Sloane and his smaller group encountered in the cemetery, where some rules and rituals would make it easier for the Spirit to be able to harm their victims and allow them to pass through their territory.
It would be the same for a certain type of popular Spirit that was summoned through mirrors, as it could follow the person who summoned it around through the reflections in the mirrors until it came out on its own.
Those types of popular scary and dare games were usually quite popular with people of certain ages closer to their teenage years, so it was a little more possible that someone would perform a strange ritual that promised a strange or scary experience.
They would not have to believe that it could work as they would just need to be curious enough to try it out or to just try it to prove that it was nonsense.
