The Castle Of Magic Mastery

Within the worlds of the practitioners of arcane, divine, thaumaturgic, and other forms of esoteric magic and phenomena, a tale of a secret place is often whispered about. Many of the greatest spellcrafters of the universe have made their way to a castle, in the mountains, yet also among the clouds, stars, and planets. Years are dedicated to perfecting their skills and gaining knowledge that they didn't even know that they lacked. The place is known only as the Castle of Magic Mastery & it is shrouded in secrecy. The people who earn the right to learn there, find themselves there, lose 3 to 5 years, and end up where they were before their visit. The people don't seem to have aged over that time and they can't say who or what instructed them, but their magical knowledge and skill has increased by an alarming degree. They find themselves with a new spellbook, that seemed to have consumed their previous books and notes with details for their review that covers the years spent studying.