The Rite of Forest Justice is a form of punishment that happens in the woods located at the Grasslands near the Tree Fort. It is administered by the Forest Wizard and forest animals in "Storytelling." After Finn intervened in the life of Teenage Bear, Mr. Fox, Boobafina, some Squirrels, and considered messing with some baby birds, a group of animals attacked him. These included the baby birds' mother, two rabbits, Mr. Fox, a beaver, Boobafina, squirrels, and Teenage Bear's mother. After chewing on him for a bit, Forest Wizard clubs Finn in the head, knocking him out.
The punishment is to "enter the Earth, and become one with the soil." This is accomplished through a blue vortex of some sort with the accused being lowered into it from a cage. While the cage is being lowered all the animals present chant "oo iggi boo boo" which roughly translates to "one with the soil". The Rite of Forest Justice is administered without a trial. It appears that the Forest Wizard conjures the vortex. Finn was being punished for "meddling in our forest inhabitants' lives and disturbing the order of the forest," but this also winds up being the reason he is freed. Apparently, the harm Finn had caused by intervening in the forest inhabitant's lives was made up for when he told them what they needed to do to improve them.