The Gym Leader of Snowbelle City, Wulfric, had called all the people in town, and he started speaking to them in his deep voice:
"The kids in town have been gone for a mighty long time. They were going to build treehouses with their Pokémon, but they should have come back by now. What happened to them?"
Nurse Joy said: "Playing outside is healthy, but for this long? I'm worried too. Let's all go searching in the Winding Woods!"
So they all went there, but they saw no track of the children, but they did saw small pieces of wood spreaded around. A Munchlax suddenly came running by.
"That's Rick's Munchlax!" a mother said. The Munchlax started crying and pointed at the trees. The townsfolk had no clue what it was trying to say. It was becoming night rather fast.
"I'm chopping some extra wood, we don't have enough with those pieces!" Wulfric said, and he sent out his Beartic. He never used it in a normal Gym Battle, but he did spent a lot of free time with it.
After a while, they came back with a large supply of wood. They set up a campfire, with stones to avoid a large fire in the forest. The townsfolk all go sleeping in their tents they brought, but after a while, they all heard creaking and slow mumbling.
A bunch of Trevenant and Phantump appear and wake everyone up. Wulfric now gets it: The children harmed the trees, so the Trevenant had cursed them. Then they died and became Phantump. The Trevenant raise their hands and a green aura surrounds them. The Phantump slowly cackle and giggle. The townsfolk then become part of the forest...
Trevenant used Forest's Curse! It's super effective!