Monster Book :D

It's called a Monster Book.
The key is called Monster Book.
When you pick up a card it says Monster Book.
Get a complete set it's called a Monster Book Set.
etc.

It's called a Crusader Codex.
The item is called Crusader Codex.
The UI is called Crusader Codex.
When you try to pick up a card you already have it says Crusader Codex.
etc.