Dark Beauty Castle is Oswald's castle at the center of the Cartoon Wasteland. Heavily damaged during the Thinner Disaster, it became one of the Mad Doctor's various bases of operation.
The Mad Doctor's Laboratory
The Mad Doctor's Dark Beauty Castle laboratory is in a room with an exposed roof, featuring various stained glass windows depicting Maleficent, Scar and Captain Hook, with a massive King Oswald window at the back of the room by the controls for a mechanical arm the Mad Doctor uses in his deadly surgeries. There are two levels—a lower level and a balcony. On the lower level below the balcony is a series of statues taken from Beast's Castle, including one of the Beast himself. On the balcony is an entrance to a Utilidor that leads to the Castle Gates.
Mickey visits this room twice, as it provides the first room he visits in Wasteland and later ends up crashing there with Oswald and Gremlin Gus in the Moonliner rocket towards the end of the game.
At the gates of the castle are two staircases that go up to the gear controls of the Castle door. The gap is blocked, but there is a projector screen located there that leads to the Utilidors of Gremlin Village. There is also a massive catapult in the courtyard where Gremlin Calvin lies trapped.
The Throne Room
Oswald's throne room is a gallery of paintings depicting Wasteland before and after the Thinner Disaster, with the most prominent of them being a large stained glass window depicting Oswald, Ortensia and some of their Bunny Children. When all the paintings are filled in, light emitting gargoyles in the forms of Victor, Hugo and Laverne can be used to activate other gargoyles on the upper levels and open up an entrance to a hidden projector screen to the Fireworks Control Tower. Another screen can be activated if switches in the walls are activated to bring the chandelier down, though this will be at the cost of being unable to restore the paintings.
The Fireworks Control Tower
From the Fireworks Control Tower, Oswald would put on elaborate fireworks shows for his fellow Wastelanders. It is where Oswald placed the stony remains of Ortensia after she was petrified by The Shadow Blot during the Blot Wars. Hallways and projector screens connect it to the three Castle towers the fireworks are mounted on.
The lowest of the three fireworks towers, the Sorrow Tower is connected to the Fireworks Control Tower by a Utilidor. A climb up crumbling staircases leads to a fireworks activation crystal surrounded by four gargoyles (from Beast's Castle). The tower has two pointed roofs—a blue one and a crumbling red one over the projector screen to the Grief Tower.
The journey up the Grief Tower goes along one continuous and gradually crumbling ramp where the Shadow Blot tries to slow Mickey down by breaking the walls. When Mickey encounters the Shadow Blot at the activation crystal, he sends in various Blotlings to attack Mickey. The roofs are similar to the Sorrow Tower's.
The Loss Tower is the last of the three fireworks towers. Instead of climbing on the inside, Mickey climbs mostly on the outside, battling Blotlings inside three arenas before arriving at the activation crystal at the top. The Shadow Blot allows Mickey to fill in the gargoyles before attacking him and bringing the tower down, leaving Mickey to take a Utilidor back to the Fireworks Control Tower after plummeting to the lower levels.
The Loss Tower is distinctive from the other towers for numerous Dragon Maleficent motifs, including various banners inside and a ring of statues upon the roof.
Epic Mickey 2
"Tall & majestic, Dark Beauty Castle towers over all. Oswald & Ortensia have worked hard to clean it up!" Disney Epic Mickey Video Game Facebook page description.
Mickey reenters Wasteland again by falling into a window of Dark Beauty Castle, where Ortensia and Gus are. Ortensia and Gus don't trust the Mad Doctor, but Oswald is convinced that they should give him a second chance. Mickey suggests they go find the Mad Doctor, when a quake starts falling, and the castle starts collapsing all around them. When some rubble comes down and separates Ortensia from the others. Mickey, Gus and Oswald outrun the rubble to escape the castle and reunite with Ortensia. Eventually all four escape by train.
The "My Other House is a Castle pin" found in Ortensia 's house and the above description seems to suggest that Oswald and Ortensia used the castle as a second home.