See also: Shadow Puppet
The Codex Umbra is a character-exclusive item that Maxwell starts the game with. When used, it sacrifices 15 health and 55 of maximum sanity to spawn a Shadow Puppet clone of Maxwell. It has infinite durability and requires 2 Nightmare Fuel to be used. For each puppet active, Maxwell's maximum sanity is reduced, similar to how Meat Effigies reduce maximum health. A maximum of 3 puppets can be active at one time and each one will disappear 2.5 days after it was summoned. If a Shadow Puppet is killed or despawns, Maxwell will get the used max sanity back.
The Codex Umbra was discovered by William Carter in August of 1904. At the time, William was boarded on a train headed to San Francisco, California from New York City. The train crashed into a broken down circus wagon, and a man of William's description was reported missing but assumed dead. However, William survived the crash with only a few injuries. While wandering across the desert, he discovered an ancient codex and was intrigued by the "terrifying" possibilities it offered.
Months later, William established himself in San Francisco and began going by the name of Maxwell. Maxwell updated his act to incorporate dark manifestations that he taught himself to summon from the Codex Umbra. He found great success in this new act and eventually hired an assistant, Charlie. During their last performance, Maxwell's act went normally until he attempted to pull "shadows incarnate" from the Codex and was instead pulled into the book by giant shadow hands. Soon, the entire act ends in disaster as both Maxwell and Charlie are violently dragged into a parallel dimension.
The Codex Umbra reappeared, still in Maxwell's possession, after he was dethroned and became a survivor. After reuniting with Wilson, Maxwell found the scientist's blueprints for an invention and offered to help construct it with assistance from the Codex Umbra. This made it possible for Maxwell and Wilson to build a portal that allowed other survivors to join forces with them.
In the Shipwrecked DLC, Shadow Puppets summon shadow Row Boats to follow Maxwell into the Ocean. The Shadow Puppets act as though they are sailing, yet the boats do not have Sails and have the same speed as a normal Row Boat. Shadow boats can only be driven by shadow puppets, and disappear when the puppet exits the boat. It is possible to enter a shadow Row Boat when not being used by a Shadow Puppet, by quickly entering it before it disappears. However, doing so results in a crash.
In Don't Starve Together, the Codex Umbra can be crafted from the Shadow Tab, using two Papyrus, two Nightmare Fuel and costing 50 Health. It is also no longer an item that can be used directly, instead it acts as a crafting station when placed on the ground, which unlocks Shadow Puppet recipes for Maxwell under the Shadow Tab. To create the puppets, Maxwell has to stand near the Codex Umbra. Creating puppets does not cost health.
- Codex Umbra is Latin for "shadow manuscript".
- It's possible for the Codex Umbra to be set alight and burn into ashes. The book will re-appear in Maxwell's inventory upon re-loading the world.
- If using the Codex Umbra reduces Maxwell's health to zero, the Morgue will show the cause of death as "Shenanigans".
- Like Abigail's Flower, the Codex Umbra floats when placed on the ground, but only if the corresponding Maxwell is nearby. If he moves out of range, the book will close and fall to the ground.
- In Don't Starve Together, the player is able to become constantly insane if they summon 1 Harvester and 2 Duelists.
- The description "Diggy diggy hole" is a reference to the song of the same name by the YouTube channel Yogscast.
- Despite being a starting character specific item, the Codex Umbra can be stolen by mobs like Krampus or Eyeplants.
- Using a Sinkhole to enter the Caves or Ruins without the Codex Umbra can sometimes cause it to duplicate in the player's inventory.
- In the Shipwrecked DLC, using a Volcano to climb onto it without the Codex Umbra can sometimes cause it to duplicate in the player's inventory.
- William Carter Puzzle #4: The Coach Ticket is dated August 15, 1904 and permits travel from New York's Grand Central Station to San Francisco.
- William Carter Puzzle #4, The Newspaper: "A passenger train struck a circus wagon that had broken down along the tracks at the Old Mill crossing. Dozens of passengers were injured, and at least one man is missing. The missing man has yet to be identified, but fellow passengers described him as a tall, nervous fellow with an English accent. A search party was convened but quickly abandoned when it became apparent that a cage full of potentially dangerous trained monkeys had been vacated in the collision. Given the remoteness of the crash site, the scorching desert sun, and the escaped animals, the missing man has been presumed dead."
- William Carter Puzzle #4, The Postcard: "Jack, The strangest thing has happened! Please discount all reports of my demise, should they reach you. I am very much alive, despite my recent misadventures. I have discovered something, a book of sorts. I have yet to decode it fully, but what little I have deciphered has opened my mind to terrifying new possibilities. I shan't say more through post - I fear it may attract unwanted attention. All will be explained when we meet. I shall continue west forthwith! -William"
- William Carter Puzzle #5: A new poster for "Maxwell the Great", a requisition for an ad in The San Francisco Call dated June 6, 1905, and a journal page recounting an encounter with a Shadow Creature after a ritual.
- William Carter Puzzle #6: New poster for "The Amazing Maxwell" featuring Charlie holding the Codex, and a letter from Charlie about their latest successful performance.
- William Carter Puzzle #8: The Final Act (Youtube)
- Cyclum Puzzles: Last page of the comic