The Enigmansion

The Enigmansion is World 4-3 in Paper Mario: Sticker Star. Here, Mario helps the steward of the mansion who is outside in a snowstorm. The steward tells Mario about something haunting the mansion and gives Mario the Book of Sealing to capture the ghosts with. The mansion's name is a portmanteau of "enigma" and "mansion".

History
In this area, the mansion steward asks Mario to capture a group of Boos by returning them to the Book of Sealing. When he enters the mansion, the Boos scatter around the mansion. Mario explores the mansion and captures all the Boos. After he finishes, he returns the Book of Sealing to the basement, but Kamek, who reveals to have released the Boos from the Book of Sealing to begin with, releases the Boos again. The Boos form a Big Boo and Mario is forced to do battle with it to return the Boos to the Book of Sealing.

Afterwards, the Enigmansion steward asks Mario to come to the left room of the mansion. Once Mario arrives, the steward gives Mario a portrait of the Forebear that the steward inherited the mansion from. Mario then has to paperize to get the portrait scrap to progress to Whiteout Valley. The Comet Piece is outside once the Big Boo is defeated. The things found in this level are an oven, a refrigerator, a stapler, a watering can, and a cake. There is a secret door that leads to the left side of Decalburg, near the shop where the Toad sells things. Once the portrait is taken to Whiteout Valley, the forebear in the portrait comes alive and lets Mario go up a ski-lift.

If Mario decides to revisit the Enigmansion after releasing the forebear from the portrait, the forebear is shown to have regained ownership of the mansion and has made the previous steward a servant of his. The forebear asks Mario to lounge with him while he drinks tea and remarks on how he rarely receives any visitors anymore. Afterwards, the steward comes in with a tray of tea and gives Mario a HP-Up Heart.

Boo Locations
There are 100 Boos to be found in the mansion:

Area Tattles

 * Outside: "What a fantastic mansion! And in such a remote spot in the mountains!"
 * Lobby: "What a huge lobby. Maybe this is some celebrity's house."
 * "Mario, you aren't just a little afraid, are you?"
 * Outside (area with Comet Piece): "Yeah, it's snowing outside, per usual. Get inside quick. It's too cold!"
 * Basement: "Ugh, it really smells moldy or something. And if paper gets moldy, it's all over."

Secret Door
The Secret Door is at the top of the rear staircase. It provides a shortcut back to Decalburg, at the Sling-a-Thing location and the Things seller.

Enemies

 * Scaredy Rats
 * Boos
 * Boo Stack
 * Big Boo (Boss)

Things

 * Oven
 * Refrigerator
 * Stapler
 * Watering Can
 * Cake

Trivia

 * In the Prima Games Guide, it claims exiting the mansion via the Secret Door shortcut will cause stickers collected in the mansion to change into others. However, this is untrue. It simply makes them reappear.
 * After clearing the mansion of Boos, all stickers found in the Mansion disappear, along with most enemies. In addition, the music changes. There are still one or two Scaredy Rats, however.
 * When talking to the Steward while he camps out, an eerie remix of the Ghost House theme from Super Mario World starts to play and abruptly ends when the dialogue is finished.
 * A slower, more eerie remix of Teresa Waltz plays as part of the background music, a song originating from Super Mario Galaxy. It also plays a quicker, more mischievous version once all the Boos are encountered in the dining room.
 * A recording of the theme that plays when the Goat sticker is obtained for the first time in Snow Rise can be found in the living room of the mansion. Both the steward and the forebear have conflicting opinions regarding the music. The steward loves it, while the forebear is iffy about it.
 * This is possibly a reference to Luigi's Mansion, since Mario needs to capture Boos similar to how Luigi has to catch ghosts.
 * Furthermore, the level has a similar setting to Secret Mine in Luigi's Mansion: Dark Moon
 * This level is very similar to the prologue since the player has to capture/save 100 Boos/Toads and there is a crumpled Toad/Boo and a set in a cupboard.