Dark Wishes

Once upon a time, in lands far far away, in fallen kingdoms and lost worlds, lived six peculiar children.
United in their mission to bring justice to their families, they ended up in the Human Realm, in a strange town named Gravity Falls, where lived eight other curious children, who called themselves the Mystery Kids. Staying in the Dark Manor, assisted by an intriguing figure, a man named Mister R, those six children must succeed in their mission to return to their homes.
PS : Title (and maybe the summary, since I suck at both titles and summaries) may change.
(Based on the fan project "Mystery Kids", as well as various folkloric legends and fairytales)