When the player is cornered, consulting the Codex allows them to review the entire timeline of the Ace Attorney history, revealing that the current case is a rhyme of history—a "callback" to a past event that holds the key to salvation.
The Ace Attorney franchise began in 2001 on Japan's Game Boy Advance before achieving global fame on the Nintendo DS. The "Codex" of the series spans several eras: ace attorney codex