Arthur's Legend 4 is a purple tome. Accordingly, it tells about the Knights of the Round Table's exploits.
In gameplay, the player can collect Arthur's Legend 4 during different Missions in certain areas. For then to obtain it, the player must use the ID points earned from completing the Mission where the Arthur's Legend 4 was picked up to identify it on the identification screen. Once secured, Arthur's Legend 4 will appear in the Gallery of Sonic and the Black Knight where it says the following:
|ID Point Price||6|