This stage is fairly simple but there are several spots where you can die very easily. You'll start out beside a Cactus, but you can only see it's top from where you are right now. Walk towards it and hit it with one of your special attacks to kill it quickly. If you take too long to kill it, it will shoot out needles at you. There will be another Cactus on top of the hill ahead. Kill it the same way. After several hills and dips there will be a Sand Monster sitting at the bottom of a dip. Either jump over it or kill it with the Spread Fireballs. Continue walking to the right and you'll find two more Sand Monsters just sitting there, along with two Birds flying above you.
The Birds are too high to bother you so you can deal with the Sand Monsters accordingly. Ahead, there will be three slightly rises in the sand. Don't walk on them. Just stand there for a bit and a Sand Snake will come out and start flying around. I don't know how a snake can fly but blast it about a dozen or so times and it will disintegrate. Right after that one, there will be another one. Kill it and grab the Full Heart ahead. A little further you'll find the entrance to a pyramid. Enter it (as if you had a choice) and kill the Skeleton waiting there. It will throw it's head and then run towards you if you take too long to kill it. You'll find another one waiting deeper inside followed by a more ancient spike masher.
The only difference is that you shouldn't go under it. You'll find that you can get out without killing yourself. Go over it instead and the next one as well. The third one is going in the opposite direction, so use your bat transformation to fly under it. When you're safely on the other side, transform back and kill the Skeleton on the far right. Change back into a bat and fly under this one too. The last one is going the other way again, so just jump over it as you did with the first two. Further ahead there will be spikes on the ceiling and a very long platform leading to the right. You don't need any special attack here, just run across and kill the Skeleton Head that appears later on. Near the end, you'll see a Heart Container under the platform.
Keep walking until you're under it and then let the platform collapse to grab it. Use your bat transformation to get back on track. Grab the Full Heart in the corner if you need it, and then fall into the hole. Kill the Skeleton at the bottom and fall into the next hole and kill the second Skeleton waiting there. As you fall down this hole, stay on the left side, and then run like hell to the far left, where there will be another hole to save you. There will be two Skeletons at the bottom of this hole. Kill them and continue to the left. Just run and don't stop. You won't die. At the end, you'll see a hand and a whole lot of darkness. It will take you to the boss.
This boss is simple to defeat but you have to watch out for the bubbles it shoots out from time to time. If you get hit by one, you can kiss one of your lives goodbye. Try to destroy the bubbles when they appear and hit Tutankhamen as much as possible. It won't take long if you're using your special attacks. After you've hit it enough times, it will start crying and some solid ground will appear below you.