So much things happening in my head as I see this. People will just drop a comment saying: "Omg this is awesome!" but I'm going to settle with a critique. Here goes.
What snaps to your eyes at the beggining are the three characters on the front. Their dynamic poses and bright colors suggests that they are joyful and adventurous characters, maybe the main cast from a story you'll make? Who knows? The fairy monkey king looks exceptionally outgoing, with its running pose and outstretched arm and hand going out in perspective, which is, by the way, very well done. The skeletal phantom horse on the bottom right of the three looks rather cute, even though it looks undead or somewhat mystical. The steam coming out of its mouth suggests flame powers, too. Finally, as for the robot, its mechanical pose is great, and it gives energy to the little robot, and I especially like its bright colors.
As I watched, maybe their colored background suggests where they came from? The monkey could come from the top background (yellow with yellow, absolutely love the Mario reference ), the undead horse comes from the evil part in the background (red) and the robot comes from the tech part of the background, with all the signs. (Blue, and I can see subtle hints in the signs: Fubukii cut off, Kernel, a part of 2013.)
Other characters are featured in the background, what attracts my eyes is the evil purple knight, at first glance you are sure it is the master overlord of the bad guys. Its mystical fell and covered face contributes to him feeling powerful. The assassin guy in the middle bottom looks somewhat friendly, maybe a weapon merchant?
I could continue for hours, describing all the details: the city patterns in the red part of the background, the sun rising at the monkey's fist, the subtle ogre in the right side of the BG, the stack of OCs that separate the scenery, the effect of sunset or sunrise from the sun...
But I'll just let people dwell their imagination on this piece. You said this piece took you months to do and you used lots and lots of pencils for it? Great job, because it paid off extremely well. For that, I give you five stars, my friend. Nice work and happy new year!