The forbidden forest is a server location near Meramar and the Haunted Manor dungeon.
Inside of it is the Scrollshop Vendor (Which can be warped to by Explorer rank and up with /warp scrollshop) who sells various types of scrolls.
It also contains the "Super Spider" mobs that are required for Abadook's quest in Meramar. These spiders can drop string, diamonds, magic items like the webshot, or magic chests.
Entrance: x=2843 z=-300