Roy's Castle is the fifth castle in Super Mario World. It is found at the end of the Forest of Illusion, and can be accessed through the secret exit of Forest of Illusion 3. The castle includes a Snake Block that Mario and Luigi have to stay on to avoid the lava below.
Mario starts in a tight space at the top of the screen. He must run across the starting platform, encountering a large pool of lava at the end. To traverse this lava, Mario must follow a Snake Block. The first Dragon Coin can be found at the beginning of the Snake Block's path. As the Snake Block moves across the pool of lava, Mario must follow it and avoid the bouncing Podoboos. After some time, the Snake Block will reach the end of the lava; however, it has not reached the end of its path yet. Mario must stay on the Snake Block and follow it across a bed of spikes. Some of these spikes are Falling Spikes. Three Dragon Coins can be found in the middle of the bed of spikes. After Mario gets past the spikes, the Snake Block will fall into a bottomless pit.
After the Snake Block segment of the castle is finished, Mario must jump onto a platform at the top of the screen and traverse across another tight space of three short platforms, this time with spikes at the top. There is a P-Switch in the middle of the space, which Mario can activate to obtain a 1-Up Mushroom in a cage of blocks at the top of the screen; however, doing this will also free an additional Gray Bowser Statue from the cage. Next, Mario must traverse across a long mechanical bridge spanning across a pool of lava, while avoiding three Podoboos and Gray Bowser Statues shooting flames at him. After crossing the bridge, Mario will find three Stretch Blocks suspended above a wide bottomless pit. Above the first Stretch Block, there is a green Switch Block that can be activated in the Green Switch Palace and contains a power-up. Mario must jump across the Stretch Blocks to cross the bottomless pit, while avoiding more bouncing Podoboos and a single Gray Bowser Statue between two blocks. The final Dragon Coin can be found above the second Stretch Block. After crossing the bottomless pit and avoiding one last Gray Bowser Statue, Mario can finally open the door to the boss battle with Roy Koopa.
At the end of that room, the brothers make it to the boss, Roy Koopa. The fighting method is similar to that of Morton Koopa in Castle #2, but the walls will shrink three times. After he is defeated, the two are able to rescue the Yoshi Egg that was trapped inside it. Like the other castles in Super Mario World, it was destroyed shortly after. By completing this castle, the player gains access to Chocolate Island 1.