Caves of the Forgotten
Seduced by Sauron, he was persuaded that he had the power to take the lands of Aman from the Valar themselves. He set out with a great fleet and led an immense army into the Calacirya, ready to do battle for the Blessed Realm itself.
Meanwhile, they themselves were imprisoned beneath the Earth where they still await the ending of the world. When the day of the Last Battle comes, it is said, they will be released from their caves, though the part that they have to play in the battle remains a mystery.