This puzzle has been my Moby Dick of puzzles for so long. It's from MellowMelon's old puzzle site and is a Nikoli-based megapuzzle with eight sub-puzzles. I'm copying the puzzle image from there so as to follow the rules for this site, and I don't know the answer to the puzzle (I've only gotten about halfway through myself, after many many hours of attempts). I would especially love to see details about the logic you used to solve the puzzle.
Original source here.
And, I'll also copy the rules over from that site:
Akari (depends on Hitori, dependee of Shikaku) The walls are not given to you in this puzzle. The black cells in the solution to the Hitori puzzle are exactly the locations of the walls. Any wall with a number represents a typical numeric clue in Akari. Any number without a wall is a fake clue and should be ignored. Light bulbs are allowed to be placed on top of fake numbers.
Shikaku (depends on Akari, dependee of Heyawake) A lot of extra numbers are given in this puzzle. Overlay the light bulbs in the Akari solution on this puzzle. Only those numbers which have a lightbulb on top of them are true clues in this puzzle. All other numbers should be ignored; they may or may not denote the correct size of the rectangle that contains them.
Heyawake (depends on Shikaku, dependee of Nurikabe) The rooms are not given to you in this puzzle. The rectangles in the solution to the Shikaku are where the rooms are. Only those numbers appearing in the top left cell of a room should be used as clues. All other numbers should be ignored.
Nurikabe, featuring Kurodoko (depends on Heyawake, dependee of Fillomino) A Nurikabe and a Kurodoko puzzle have been superimposed on each other. The solution to the Heyawake puzzle and the Kurodoko puzzle are identical. Each number in this puzzle is the location of a clue in both the Nurikabe and Kurodoko, and the number is the sum of the clues in each of the puzzles (i.e. if there is a Nurikabe 1 and a Kurodoko 6 in the same space, a 7 will appear in this puzzle).
Fillomino (depends on Nurikabe, dependee of Country Road) A lot of extra numbers are given in this puzzle. Overlay the Nurikabe solution on this puzzle. All numbers covered by a black cell in the Nurikabe solution are liars and are not the correct number. All numbers covered by white cells are truth-tellers.
Country Road (depends on Fillomino, dependee of Corral) The rooms are not given to you in this puzzle. Overlay the Fillomino solution; it gives the shape of all of the rooms. Each room will contain no number or one number, which functions as a standard Country Road clue for that room. The number can appear in anywhere in the room.
Corral, featuring Masyu (depends on Country Road, dependee of Hitori) The grid is filled with Corral clues in black or white circles, but not all of the Corral clues are correct. Overlay the solution to the Country Road puzzle on this one. Cross off all of the circled numbers for which that colored circle would not be a valid Masyu clue in the Country Road solution. All of the numbers that are left are the clues to the Corral puzzle. (the numbers that are crossed off may or may not be correct)
Hitori, featuring Slitherlink (depends on Corral, dependee of Akari) A Hitori and a Slitherlink puzzle have been superimposed on each other. The solution to the Corral puzzle and the Slitherlink puzzle are identical. The Slitherlink puzzle gives a number in every square, just as the Hitori does. All of the Hitori clues are numbers from 1 to 10. Each number that appears in this puzzle is the units digit of the sum of the Hitori and Slitherlink clues. For instance, in a space where the Slitherlink has a 3 and the Hitori has an 8, a 1 would be written in this puzzle.