The Royal Castle is the first level in Super Luigi World: The Big Adventure. The goal of the level is to find Toad and bring him back to the Royal Garden. Unlike other levels, it has no boss. Most of the mechanics are introduced here, like power-ups and springs.
The first part. Luigi must bring Toad back here. The only working door connects to the Royal Foyer. There is a single enemy here, which is a Goombo. No ? Crates appear here.
Where most of the Toads are. There are many doors, but most of them are locked. There are also alot of Goombos and Bombshell Koopas. Mario can also be found in a pit of sticky quicksand, requiring an Unstickshroom to get unstuck. There is one ? Crate here.
A large chasm appears in this room, along with Blue Toad. Above him is a chandilliar which lowers after his quest. You must go across the chasm using platoforms and reclaim the lightbulb. Afterwards, you must travel back and complete your quest, jump on the chandiliar and hop over the wall. No ? Crates appear.
The second part of the Ballroom. After arriving, you must save another Blue Toad from some Goombos. Afterwards the Toad gives you a key to Floor 2. A single ? Crate is here.
The second floor. It has 5 doors, 2 of which are locked. The middle is slighty lower then the round area with doors, and a ? Crate appears in it.
On the first floor, but you can only enter it through the second floor. It has two levels, with stairs connecting them. A Red Toad is there, with waiter clothes on. You have to play a minigame, whcih includes throwing dishes at tables. After completion, the Red Toad awards you with a key to the Bathroom. About 3 ? Crates appear, the most of any area in the Royal Castle.
A small room on the second floor. A Piranha Plant is coming out of the sink, and you must defeat it for a key to the Basement elevator. No ? Crates appear.
A small closet that has nothing in it until after you beat the game 90% or more, which cause Shy Buy to appear. A ? Crate appears, but only if you buy from Shy Buy, in which case it has the item you bought.
A large area with alot of Warp Pipes, platforms to jump on and bridges to go across. 4 Yellow Toads appear in different areas, offering Key pieces. The first one needs you to defeat 10 enemies. The second asks you to play his minigame. The last two need you to find them either a coil or gear, depending on the Toad.
A small, white area where Proffesor Toad lives. He asks you to collect 3 ingredients for his new potion. After doing so, you can use the potion, and you are then given a super-spring move. No ? Crates appear.
After using the super-spring pad in Floor 2, you can reach this Floor 3. There aren't many doors here (just 2), but one of them is important. Another ? Crate appears in the middle.
Another "empty" closet. If you bring Toad here, he will reveal a elevator to the first floor, making his quest much easier.
A cold freezer where Toad is frozen. You must thaw him by pressing a button. He will thank you, and Luigi explains the situation. He then must carry Toad to the Royal Garden.
Mario appears in the first part of the level, the Royal Foyer. He is stuck in quicksand, and need Luigi to get him an Unstuckshroom. It can be found with a Goombo near the door to the Ballroom. The reward is a key to the Ballroom.
He appears in the Ballroom. His quest involves you jumping across the platforms in the chasm to get the lightbulb, then hop back and return it. He then brings down the chandilliar, and Luigi can jump across it to get to the second part of the Ballroom. Another Red Toad appears on the other side of the Ballroom, who is being attacked by Goombos and Bombshell Koopas. After defeating them, the door to Floor 2 is unlocked.
He appears in the dining room. To get his key, you must complete the "Dining Dude" minigame.
4 Yellow Toads appear in the Basement, offering pieces of a key. The first one asks you to defeat 10 enemies. The second wants you to play his minigame, "Nuts 'N' Bolts". The final two need you to find them either a gearl or spring, depending on the Toad. These items can be found throughout the Basement.
A Toad in the Lab. He needs you to find him a Garlic Mushroom, a Eye Flower and a Koopa Leaf. Collect these and he will bake you a potion, which allows you to use the spring-jump.
His reward is important: entry to the next level and him as a playable character. His quest is also easy, which is to carry him to the Royal Gardens.