Make sure you have shut off everything in the Waterfall room before you push the buttons at the Power Box. Click combinations until both symbols for the Waterfall are green, then go back and open the floodgate. Watch your head.
There is an incomplete "chessboard" in the fireplace-elevator, which will take you down to the two books. Number the fields on the incomplete "chessboard", starting at the bottom far left corner, going left to right: 1 to 8. Then for the next row: 9 to 16, and continue the pattern with 48 in the top far right corner. Note: Try pressing: 9-34-6-16-30-19-20.
Serenia is graphically the most incredible aspect of this game. Create a save point in Atrus' Library. You may want to visit and re-visit Serenia. Earth, Air, Fire and Water, and you will be a different Child if you keep going through. The best part is where you finally get into Dream. Note: To Harmonize The Ancestors, ask yourself: where do all colors begin? Note: In order to get to a new version of Serenia, you must restart the game. It is easy enough to take shortcuts through Haven. You must at least go through Haven, then Link back.
This is a very tough puzzle. It, like the Mangree puzzle in Haven, is set up with a clock ticking. After figuring out which combination on the three cables makes each crystal begin its vibration time it is a matter of time. When you know those, watch every crystal carefully and see how long it takes for its vibrations to stop. Four codes, four crystals, and three cables with twelve markings apiece on them. Start the longest-vibrating crystal first. This will give you about 45 seconds to set off the others. Longest to shortest is the key. The main problem is keeping track of where to set the sliders on the markers without making a mistake. You can try marking the screen with something that will erase easily to keep track.