A little thing I noticed.

Yeah, I was thinking about the same thing. I doubt they originally planned several things which are in Maple now, such as Pink Bean, etc.

In fact, I'm pretty sure that, at first, they didn't think that Maple would've become such a huge game with such a great income. If you listen to the first BGMs, for example, they weren't as 'complex' as the latest ones. The concept of the game wasn't really complex either at first, but when they realized that it'd have become one of the most successful games in South Korea and in the rest of the world, with a great income for them, they hired more development staff, adding more and more concepts to the game, some of them which can be considered kind of 'complex', and developed better-looking areas, and better BGMs, to make the huge userbase happy.

What I'm saying is, yeah, they probably didn't plan to add many of the things which are now in Maple to begin with. The entire Black Wings plot only started with the Cygnus Knights only. The Black Magician stuff started with Magatia, and maybe it had other little references in Victoria Island quests (?).

So, who knows if they originally planned to do something with that castle in the background of the El Nath Dungeon.. I highly doubt, since, yeah, Zakum's background is named "FinalFight", so that could make one think that they planned to make Zakum the final boss at that time. OR it could just mean that it's El Nath's final boss.

So many questions and no answers.. It'd be great to be able to ask to a developer of the game questions like these.

Maple has always made excessive use of the "Noodle Incident" - that is, events in the past that are referred to but never, ever explained in detail. It's arguable whether they set these up well or not, but as time's gone by more and more are finally being made use of. The most obvious is Tristan and Balrog; I have to admit when I first looked at it I never thought they'd come back and explain it. Now not only do we have the Balrog boss at the bottom of sleepywood and all that ties to it, but even the Dual Blade's storyline stems from that. Alcaster is a walking talking mess of Noodle Incidents: Between his involvement in Magatia (Why did he leave? What became of the 3rd faction?), the Book of Ancient and the war that quest mentions (war against the black mage?)... Athena being an Elf? How come she's the only one in the whole game?

Naturally as some are filled in, new ones spring up, especially in regards to Elin and Neo City (Elin alone has a plethora of questions that spring forth from it, not the least of which deals with a mysterious locked room that's been in the data from day 1 and still has no use. Neo City has dozens of unused NPCs with scripts attached who don't respond to anything.) It's just a part of storytelling, especially when you've got a group of people working to put it together, with some coming and some going all the time. The Balrog thing was just a simple backstory for a quest chain to one person, but someone else came along and thought it would be interesting to investigate. Who knows, maybe that's happening now with the Nath castle there. The original designer just put it there to lend atmosphere, someone new has come in and felt it needs explaining. One of the most frustrating things about the lack of Masteria updates is that the first design team went to great pains to leave TONS of noodle incidents all over the place, and so far only a tiny fraction of them have been revealed.