A relic of Mordenkainen that Arkis believes might be a book. It's been lost to history and seems to be actively hiding itself. He has spent a long time searching for mentions of it.
Corruption says that the book contains a record of every evil thought that was ever thought. He wants it for inspiration. He's lying through his teeth.
Sort of Unknown. It's with Corruption, wherever he is. It was in the Magus Vault in Mordenkainen's Tomb.