Boo's Horror Castle

Boo's Horror Castle is one of the seven boards of Mario Party 9. The players's default vehicle is the Flying Carpet. The unlockable vehicles for this board are the Float Mattress and the Boo Blanket. The mid-boss of this board is a giant Dry Bones, fought in a small fort on a flat tower on the side of the castle. The stage boss is King Boo.

Layout
The players begin just outside the castle. They ride up the steps and go through the front door, arriving in a large antechamber. The players eventually leave through a door on the left side of the chamber, emerging on a walkway that leads to the mid-boss fortress. After the mid-boss (Dry Bones in solo mode) is fought, an ethereal blue trail appears in the remains of the fortress, allowing the players' vehicle to enter the castle again.

After passing through several more rooms, the players emerge from the castle once more, using another glowing trail to reach the roof of the building. The players must navigate around the roof to reach a sealed Bowser Gate; to open the path, the captain must roll a number equal or higher to the number displayed on the gate. If they fail to breach the gate, the group must go around the roof again to get another chance-fortunately, the gate's number requirement decreases by 2 after every failed attempt to open it. Beyond the gate, players ride one last energy path to reach the tallest tower in the castle, where they must battle a Stage Boss (King Boo in solo mode) to complete the board.

The main gimmicks and obstacles in Boo's Horror Castle are the Boo portraits scattered around the board. When the players pass a portrait, it spawns a Boo at the end of the turn. These Boos follow the players, moving three spaces at the end of each player's turn. If they intersect with the vehicle, the current captain will lose half of their Mini Stars and the Boo disappears.

Several branches in the path lead to well-lit areas that the Boos cannot enter, providing temporary safety from the wandering ghosts. However, this can cause the Boos to actually end up in front of the players, forcing captains to limit their movement, and becoming especially difficult if other Boos are still pursuing the vehicle. Additionally, Boos summoned in the first area disappear once they reach the mid-boss fort, but the Boos in the second and third sections of the board simply end up circling the roof until they cross paths with a captain or the group manages to pass the Bowser Gate.

The characters ride a floating object on this board, either a carpet or a bed. The vehicle available from the start is the Flying Carpet. The Float Mattress and the Boo Blanket can be purchased from the Museum for 200 Party Points each.

Scaredy Rat Race
In this Captain Event, a Scaredy Rat appears and steals two, three or four Mini Stars from each player depending on how many players there are. The players give chase, still riding their vehicle. The Scaredy Rat rolls a 1-2-3 Dice Block to escape along a course featuring several Dash Spaces, and the players roll standard 1-6 Dice Blocks in an order determined by the captain. If a player catches the Scaredy Rat, that player earns all of the stolen Mini Stars and the event ends. The event also ends if the Scaredy Rat reaches the end of the path and escapes, meaning that no player recovers the Mini Stars.

Deck Dry Bones
To defeat Dry Bones, players must memorize the colour and symbols on several cards as they flip face-down. When Dry Bones appears on a platform, the players must choose a card whose colour matches that of Dry Bones' platform. Successful matches damage the enemy, earning players three points per hit; unsuccessful matches do nothing.

As Dry Bones takes damage, he summons more platforms, increasing the difficulty of choosing a matching card. He also begins adding cards with his own face on them; players who choose these cards get whacked with a bone, costing them a point. When Dry Bones loses half of his health, he begins swapping rows or columns of cards after they flip over, attempting to further confuse the players.

King Boo's Puzzle Attack
King Boo's battle requires a quick eye and a fast hand. The players must try to line up multiple images of the same power-up. Once three or more are in a row, the items will fly at King Boo to inflict damage. The player will get one point for each power-up fired this way, with extra images in the line doing extra damage (e.g. if four Fire Flowers are in a row, the player will get four points). If the player lines up three Lightning Bolts, they will unleash a powerful attack, giving the player ten points and removing three points from all other players.

Once King Boo's HP drops below half, he will send Boos to harass the players. The Boos bob up and down, trying to chase the players' markers. If the Boos capture a player's marker, it will freeze and the player will have to shake the Wii Remote to break out. The ghosts can be briefly dispelled by lining up a Lightning Bolt attack, but King Boo will quickly replace them.

Uniquely, this is the only boss minigame that awards ten points (instead of three) to the player who lands the final blow on the enemy.

Official Description

 * Flag of USA.png "Spooky... This haunted castle is infested by Boos and Scaredy Rats. Look sharp!"
 * Flag of Europe.png "As you and your party make your way through Boo’s Horror Castle on a floating bed, do your best to stay ahead of the ghostly Boo - who gives chase once you pass his portrait and helps himself to half of the Captain’s Mini Stars if he catches up."