It is a remix of the castle songs used in Wonder Boy III The Dragon's Trap, a game from the old Sega Master System. It is actually an official song used in the new remake that's released now, coming to Steam in June. And I really love the music from it!

Man, you are just on FIRE, Congrats. By the way... Was that song a customized/remix of a Sonic Song? I can't put my finger on it, but I'm fairly sure I've heard it from a Sonic game... Maybe Generations? But that's just what I heard. I might even be way off.
But anyway, keep going!