A Neoquest WMG page will exist.
There is something behind that door.
- The fact that eight years' worth of members attempting, collaborating, discussing, and ultimately failing probably means that there is no way to get in, but it doesn't have to mean there's nothing there...for all we know, there is coding that would kick in if one were to actually enter, and only the game's creators know what it is. (Actually, from what I remember about the TNT of that era, it's surprisingly plausible...and you can just bet they're still giggling over their little secret...)
- If there is something there, there's only one person who knows. Adam and Donna have said via Reddit that the same person created all of Neoquest and they don't know any more about it than we do.
Jahbal was trying to cut a deal with Rollay to destroy Neopia City.
- There's stated reasons behind all of the monsters running around the jungle ruins. All of them except the jungle knights, that is. All of the jungle knights/lords/etc. are chias, and the only other chias in the game are Jahbal's servants. Jahbal knew that the further his monsters travel, the weaker they become. He also knew that the jungle ruins held powerful creatures inside, so he sent an envoy to convince Rollay to sack the one city that was too far away for Jahbal to destroy. The lizards in the basement destroyed any knights that went down there, which is why they're stuck in the upper dungeon.