Darkness (Duel World)

Darkness is the fourth Duel world in Yu-Gi-Oh! World Championship 2008.

This world introduces the player to Tag Duels. Neo-Spacian Dark Panther will explain the mechanics of Tag Duel to the player and also puts the player in a practice Duel to demonstrate. After this, he'll become the player's tag partner. He can be switched out for any other Duelist (excluding stone monument or Tag Duelists) the player has beaten at least 10 times, or a Ghost Duelist.

Ground half[]

There are several teams waiting for the player. As with the other worlds, the player must defeat them at least once to progress the story. Defeating each of them 5 times will unlock the respective team in the newly added "Tag Duel" mode in World Championship Mode.

Mythical Beast Cerberus and Darkblaze Dragon (unlocks Decoy Dragon and Different Dimension Dragon)
Goe Goe the Gallant Ninja and Lady Ninja Yae (unlocks Sasuke Samurai and Sasuke Samurai #2)
Vanity's Fiend and Vanity's Ruler (unlocks Machine King and Perfect Machine King)
Dark Mimic LV3 (gets the player in a 1v1 Duel against it; unlocks nothing)

There's Renge, Gatekeeper of Dark World waiting at a corner. The player talks to him, and each time the player does they will find themselves in a Tag Duel with some of the Dark World denizens, and will also have to ante a card with "Dark World" in its name. The teams are:

Kahkki, Guerilla of Dark World and Zure, Knight of Dark World
Goldd, Wu-Lord of Dark World and Sillva, Warlord of Dark World
Brron, Mad King of Dark World and Reign-Beaux, Overlord of Dark World (defeating this team unlocks them in Tag Duel mode)

Also, since the player is wagering a card, the player well also get a Dark World card each time the player defeats a team. Now, once the player is done beating these three teams, the player will Duel every team available once more (appears that they have been brainwashed), and then a castle will appear.

After clearing the Gate, Nurse Reficule the Fallen One will randomly appear, and she may randomly change the appearance of the player's face for 500 DP. The only ways to change or revert the result is to either wait for her to reappear, or to close the game before it can save. The player can change to any of the 10 faces that the game originally offered, or a special variant of those faces for a total of 20 possibilities.

Treasure chest[]

Once in a while, there will be a treasure chest around the area. The treasure chest can either contain nothing, DP, card, or a Duel with Dark Mimic LV3.

Castle[]

The player visits it, and the player will be greeted by Gogiga Gagagigo and Mobius the Frost Monarch. After the player beat them, and the player will afterwards be challenged by Vampire Lord and Vampire Lady. Defeat both teams and they unlock themselves in World Championship Mode.

Alien Infiltrator arrives, grumbles about the player undoing the brainwashing, and disappears into the sky.

Sky[]

The map has expandeded - the player heads up into the skies and takes on more teams.

Harpie Queen and Harpie Girl (unlocks Harpie Lady 1 and Harpie Lady 2)
Metal Shooter and Satellite Cannon (unlocks Adhesive Explosive and Blast Sphere)
Lich Lord, King of the Underworld and Alien Hypno (unlocks Alien Mars and Alien Psychic)

UFOroid also appears on occasion. Correctly guess the symbol it is thinking of and it will give the player a card.

After beating each team once, Alien Infiltrator and Alien Shocktrooper will challenge the player to a brainwashing Duel - this one is computer-controlled. It may take the player a few tries to beat them. After the player beats them, they unlock themselves, and reveal the gate to the next world.

Gate[]

When the player goes to the next gate, the player is to face the guardians, Dark World Guardian - Gigori and Underworld Guardian - Moley, and their five Deck combinations. The player beats three to proceed, and beats five to unlock Aster Phoenix in World Championship Mode.

Stone Monument[]

The stone monument will appear once the player has defeated every team five times each. The stone monument has a carving of Vennominaga the Deity of Poisonous Snakes. The player needs to summon Vennominaga and use the effect to win the Duel, in order to unseal it. Beating the monument will unlock Professor Thelonious Viper in World Championship Mode.