The only requirement for this dungeon is a heavily forested area, meaning it can be dropped into just about any world. It ties in heavily with Fey creatures so I suggest a hook regarded some ancient relic hidden away by the Fey that must now be retrieved. Perhaps the former ruler had an agreement with the ones who hid this relic away, but a new ruler has taken the seat of the Emerald Queen and all agreements have been terminated.
The current Boss Monster listed on this page is "The Emerald Queen" [Fey]. In order to improve the usefulness of this field, I recommend changing this name to represent the specific species of the Boss Monster (Nymph, Dryad, etc.). Having not read or run this adventure, I can't say what creature type she has in the Monster Manual.
In the event that a user is specifically interested in "The Emerald Queen", they can still find this adventure using the basic search engine, as the term is referenced in both the Title and the Description fields.