You find out that the tower belongs to Yen Sid, the great wizard from Fantasia, and king Mickey's master! He tells you some really important things, so pay attention.
He tells you to read a book, but it's not necessary, since it contains mostly useless information. You then learn that the white creatures you fought against are the Dusk, a kind of Nobody. Nobodies are created when a strong hearted person turns to a heartless, the empty bode becomes the Nobody. The guys in black cloaks, like Axel, are from Organization XIII, a group of the most powerful Nobodies, who controls the others. He also tells you that the worlds are separated again, so you have to re-open the ways through them.
You'll then meet the three good fairies from Sleeping Beauty, Fauna, Flora and Merrywheater, who gives you new clothes, wich have special powers. They give you one of this powers, but the others you'll have to acquire during the trip. With the one they give you, you become capable of using two keyblades. You also get a new keyblade from Yen Sid, the Star Seeker.
Then, you three get on the gummi ship, and Chip and Dale (I hate them they're so annoying) tells you that Twilight Town has disappeared. Meanwhile, back in the tower, Maleficent's crow appears, and the fairies start to remember her. As a result, she is reborn, from her empty cloak, just like in Sleeping Beauty. The fairies run to tell Yen Sid, and Maleficent laughs. You then go to the only world available: Hollow Bastion.