After getting past Ravio's blockade, you find Osfala, who goes into the Eastern Palace. Follow him to make sure nothing happens to him.
Eastern Palace 1F
In the first room, step on the switch in the bottom-right corner of the room to open the door there. Then go through the door and pick up the rupees there.
Go back to the last room and use the bow and arrow to shoot the crystal switch that is across the gap in the middle of the room. A couple of floor panels fall down. Go north up those panels and through the north door.
In the next room, turn left and use the bow and arrows to hit the crystal switch to the left. Then go to the last room and through the northwest door to reach the chest. It contains a red rupee.
Now go back to the last room and go through the middle north door again. There is a jelly-like monster here called a Popo. Get rid of it and exit north.
In this room, you can see some balls rolling south. Go down the stairs, then carefully go north, avoiding the rolling balls. Sometimes a huge one will roll toward you. Try to hide in the small gaps on the sides of the path. When you reach the top, go west, then south and up the stairs.
There are some rupees up above, but when you get the blue one, a piece of wall comes out and pushes you down into the gap next to the are where the balls are rolling.
Back in the upper walkway, walk east across the grating, then go north up the narrow path to step on a switch that unlocks the east door. Go through. Go east and walk onto the piece of floor that is rising and falling. You can reach the room south of this one if you wait for the platform to go to the bottom, then walk south to the next room. In that room, you find some fairies, and some rupees. You can use the bug net to catch the fairies. If you have an empty bottle, you can put a fairy into it after catching it with the next. A fairy in a bottle will revive you if you lose all of your hearts. The fairy goes away after it does that.
Back in the room to the north, stand on the rising and falling platform. Use the bow and arrow to activate the two crystal switches. You have to shoot the one on the right when the platform is at the top, and shoot the one on the left when the platform is at the bottom. The crystal switches are only active for a short time, so run to the northeast corner of the room to walk on the platforms and reach the chest. It contains a small key. Use the northwest door to exit the room.
In the room with the rolling balls, use the northwest exit. The door shuts behind you, and three Popos come out of the ground. After you defeat them, four more appear. After you get rid of those, a chest appears, but you can't reach it.
There is a secret passage under the chest. Walk south through that passage to get to the next room. Step on the switch in the bottom-right corner of that area. A chest appears that contains a red rupee.
Go north to the previous room, then use the southwest exit. Go up the stairs, then go around to the north door. Go through to reach the chest that appeared earlier. It contains the Compass.
Go back to the last room and step on the switch in the northeast corner to open the east door. Go through it.
Go to the north wall of the rolling ball room and use your key in the north middle door. You'll go up to the next floor.
Eastern Palace 2F
The door shuts behind you. Step on the switch in the middle of the room to wake up the Armos Statues. Get rid of them. A green portal appears in the middle of the room. If you step into it, you go back to 1F. You can use this as a shortcut if you need to leave the dungeon to heal up.
Continuing from the room in 2F with the green portal, go east. There are traps in the wall that spit arrows at you, so be sure to hold up your shield by holding the R button. (If you don't have a shield, you might want to buy one from the Kakariko item shop.) Make your way to the southeast corner of the room. There is a Popo in the southeast corner that appears when you get close. Once you kill the Popo, a chest appears farther north in the room. After you open it, the mouths on the north wall will spit arrows at you, so be prepared to get out of the way. The chest contains a potion ingredient. Once you collect enough of the potion ingredients, you can take them to the Witch's Hut (north of Eastern Palace) to make some potion.
You could step on the switch at the southwest ledge in this room to open the south door, but there is more to find in the northwest room of 2F, so go back to the green portal room of 2F.
Back in the green portal room on 2F, go west. There are many rolling balls in this room. Carefully go to the left side of the room, then step on the switch. Stand on it until the stairway has come all of the way out, then run up it. A large rolling ball comes out in this pathway, so be careful to wait until it rolls past before you run east.
Go down the stairs. There is a safe area north of the raised platform in the middle. The switch on the right just makes the stairs go away, but there is a hidden switch under those stairs, so when the stairs have gone into the wall, run up to step on the hidden switch. This makes a chest appear on the left side of the room. It contains another potion ingredient.
Now go to the southwest corner of the room and step on the switch there to open the south door. Go through.
In the next room, go to the south part of the room, then go up the stairs. Go north up the middle of the room and you find a big locked door. Shoot an arrow west of that door to hit the crystal switch there. That makes a platform on the left side start rising and falling.
Go south, then go east down the next stairs. From there, go northeast. Use the bow and arrow on the crystal switch left of the door. This makes a platform rise and fall to the south. Step on it, then shoot an arrow north when the platform is at the top to hit the crystal switch to the north. This makes the east door open. Go through it.
In this room, there are four crystal switches down below. You have to stand on a moving platform and use the bow and arrows to shoot the crystal switches. Also, there are mouths that spit arrows at you, so you will need to be prepared to dodge them or block them with your shield. When you hit all four crystal switches, a chest appears on the right side of the room. It contains a key.
Now go west and use the key on the west door. (If you can't reach the west door, go to the big locked door in the middle north of the room and shoot the crystal switch to the left.) Go through the western locked door.
The door locks behind you and three Stalfos wake up. Stalfos will jump away from your swinging sword, so you can either hold the B button to poke them with your sword, or just back them against a wall and hit them there. When they are all gone, the big treasure chest goes down to your level. The southeast door also opens. The big chest contains the Big Key, which allows you to unlock that huge door in the middle of 2F.
Before you go to the big door, use the southeast exit that just opened in the room where you got the Big Key. There is a crystal switch in that small room. Hit it to reveal a switch in the northwest corner of that room. Now go back to the Big Key room and use the east middle door.
Stand on the platform that is going up and down. Shoot an arrow north when the platform is at the highest point. The floor will change, allowing you to reach the big locked door. Go up to the big locked door and press A to open it.
Yuga is there. He turns Osfala into a painting. Then it's time to battle him.
Stay on the opposite side of the pit from Yuga, and shoot him with your arrows. He will sometimes hide in the wall as a painting, so don't try shooting him then. After you hit him enough times, he gets angry and starts throwing energy balls at you, but only if you give him time to do so. Try hitting him before he can shoot you.
After a while, Yuga is too badly hurt to keep fighting, so he turns you into a painting on the wall. Is this game over? No! Somehow, Ravio's bracelet gives you the power to pop back out of the wall and become a painting again whenever you choose. Press A to get out of the wall. Then take the Heart Container in the north part of the room.
Escape as a Painting
To escape, you have to merge with the wall, then slip out through the thin opening in the north wall. Keep in mind that you can only be a painting for a limited time until the purple energy bar runs out, then you'll automatically pop back out of the wall. At any rate, slip through the crack in the north wall as a painting.
You'll have to keep walking around the outside wall until you reach a ledge. When you reach a ledge, you can see a pot with a purple glow coming from it. This contains energy to refill the purple energy gauge.
You want to go to the east side of this area. From the room where you fought Yuga, merge with the east wall and approach the crack in the wall from the right. Then you can go to the east side of this area. After you pop back out, drop down to the ledge below you to the north. Merge with the wall there and walk along the wall until you get to the other side. When you pop out there, you will fall to a lower level. Merge with the wall after you fall, then walk along the wall again. You will collect some green rupees. When you pop out on the other side, walk east to find a chest that contains a silver rupee!
Now merge with the wall and walk along it to the ledge on the west side again. There is a moving platform to the west. Step on it when it comes up to your level. Then when it goes to the bottom, go south.
Outside Eastern Palace 2F
You're now on 2F. Walk south onto a platform that extends and retracts. When it retracts, you have to merge with the wall to avoid falling (unless you are quick). After you get off of the moving platform, go south and then east to the next area.
Outside Eastern Palace 1F
To make any progress, you have to merge with the piece of wall that slides back and forth to the right of you. Merge with it, then walk to the other piece of wall to the right that slides over to connect to it. Wait for this second piece of wall to slide to the ledge, then pop out of the wall.
You can see a crack in the wall to the east, but before you go into there, merge with the wall north of that crack. Walk along the wall to reach a chest that contains a purple rupee.
Go back to the crack in the wall and go through. When you reach the indoor area, pop out of the wall, then walk to the east side of the room and go through the crack there. Open the chest on the other side to get a silver rupee.
By now, you have found all of the secrets in the Eastern Palace, so you should leave. Outside, you find Sahasrahla and tell him what happens. Then you hear a rumbling, and Sahasrahla says something bad is happening at Hyrule Castle.
The two of you automatically go there and discover that the castle is surrounded by a colorful magical barrier. Sahasrahla speaks of the legend of the hero who found all of the Pendants in order to get the Master Sword and break the barrier at the castle. Sahasrahla despairs that one of the pendants is trapped in the castle with Zelda, but then you reveal that she gave it to you.
Sahasrahla realizes that you must be a new hero. He says that you have to get the other two pendants. One is in the House of Gales, and the other is in the Tower of Hera. He marks the two locations on your map, then gives you the option to save your game. He will go back to Kakariko Village and research who the other descendants of the Sages might be.
When you stand near the castle, the paintings in the walls become enemy soldiers. You'll find tough evil soldiers in many areas of Hyrule now.
There is a lot more you can do now, so you might want to take some time to explore Hyrule before you tackle the House of Gales or the Tower of Hera.