This is an acorn of mass destruction. It’s stored in a small box with room for six but only containing the one.
A strange, mystical box, with many rumours attached, that does not want to reveal its secret…
Teenagers who run away from home to live in the wilderness may become feral. As they become more and more feral, they gain some supernatural powers (a la Peter Pan - ability to fly, things they imagine come true - possibly quite powerful), but at the expense of their humanity and ability to speak, comprehend complex subjects, etc. Maybe they have a leader: the most feral of them all.
A regression into a fantasy childlike state.