After learning that Maleficent was killed, Pete visits Villain's Vale, to see if it was true. He finds an empty fortress, but is soon greeted by a Diablo and a resurrected Maleficent. She begins to use it as a base of operations, even though now there are only two in her league.
When Sora and co. first arrive in Hollow Bastion, at the base of the Vale is a swarm of Shadow Heartless. Leon and the rest of the Hollow Bastion Restoration Committee wish to restore the city but need to get rid of the Heartless first. After the Battle of the 1000 Heartless, the base of the Vale is no longer surrounded by Heartless. The Heartless were probably amassed together by Maleficent and Pete for their army and then used to attack Hollow Bastion. The Heartless, however, sided with Organization XIII and did not finish attacking the city.
Villain's Vale appears in several flashbacks (or rather, flashforwards) seen in Timeless River. As Maleficent treats Pete badly after his failure, the latter begins wishing he could return to the old days when he captained the Steamboat Willie. In response, the worlds gave Pete a doorway to his past to atone for his mistakes. He shows the door to Maleficent, who orders him to go to the past and destroy the Cornerstone of Light so that they may take control of Disney Castle in the present.
The fortress also acts as the driving force of most of Maleficent's actions during this game. After losing Hollow Bastion to the Hollow Bastion Restoration Committee, she deems the crumbling fortress unworthy, and begins searching for a new, grander castle in which to rule, setting her sights on both Disney Castle and the Castle That Never Was.
It can now be seen from the Bailey of Radiant Garden in the distance, and the Ravine Trail and following maps lead one closer to the fortress from the town. In Kingdom Hearts II, if the player uses the Reaction Command on the left balcony in the Bailey at the Radiant Garden, the resulting text says that he can see the "Villain's Vale, where Maleficent once resided." Another mention lies in Jiminy's Journal; in the story section, Jiminy states "In Villain's Vale the Heartless were swarming, as Nobodies darted about." The Dark Depths are very close to it, and gives a good view of the whole citadel. Both Xemnas and Sephiroth stand on the edge of the cliff, looking over the fortress at different points in the game. In Sephiroth's case, he overlooks Villain's Vale preceding his battle with Cloud.
The Villain's Vale is a large fortress comprised of several spindly, crooked, golden-brown towers topped with black cone towers, also crooked and spindly. It resides over what appears to be the ruins of a tiny village of ramshackle stone buildings, and its facade is dominated by a giant Heartless emblem.
Inside, the only place ever seen is the the tower where Maleficent and Pete speak. It's a seemingly open room with a balcony looking back at the main Hollow Bastion area. On the inside, the walls have a sliding water effect, but not much more is seen.