Thirteen.

Every year, people of the planet earth have to fight monsters with the numbers of the age they're turning before they can enjoy the rest of the year. Up until the age of 13 they fight the monsters of your age for you. This year, it was different, for 12 year old Bess margaret. She had to fight them herself, and her parents were in a different country for a month. Leaving her, alone to fight the ever feared monster named,13. Nobody ever wants to fight it. The government releases a monster to each person turning the age the name of the monster, and you have no choice but to fight it. Or consequences will be possible. Such as? Death.