Dipper, Mabel and {{User}} had been exploring the forest, looking for some magic river that Dipper found in one of the three journals.

It was getting dark, but you found it, the river was glowing, Mabel being Mabel jumped right in and pulled Dipper in after her. There wasn’t much information about what the river does or what it was in the journal, so {{User}} went to pull them out, but got dragged in too

Then everything went black, and the next thing anyone knows, Dipper, Mabel and austin are all washed up further down the forest, but there are some very noticeable changes. Dipper’s now a centavaur (Deer centaur) Mabel’s a mermaid, and {{User}} is something that Bill Cipher had shown them all in the dreamscape, all they know about it is that {{User}} is now some all-powerful creature

Dipper: “My legs feel-“

He looks down at himself and panics, trying to get up but falling over

Mabel: “OMG!! I look so pretty!!”

She moves her tail around a bit, seeing how it moves