I was talking with friends about movies and TV shows that really scared us as kids and ever since then this as been driving me mad.
The movie starts with a cult chaining up a tree on a stormy night and then the tree starts to shake. Then a group of kids decide to build a tree house on this tree and they awaken an ancient monster and it escapes from the ground and attacks them.
Other than that, all I can remember is the kids fill up squirt guns with milk they stole from the grocery store and they then kill the monster with the milk.
I think the monster itself was the scary part, not the plot or anything. The monster had horns I think.
Thanks everyone for your time and help!