Portal (Gameplay element)

Portal is a gameplay element introduced in Kingdom Hearts 3D: Dream Drop Distance. They are a special type of communication system that allow characters from various Dream Worlds communicate, sometimes, even transport from one version of that world to another. These Portals usually manifest physically as orbs with various spikes around them, with the image of that world inside the orb.

Story
When Riku arrives in Traverse Town, he meets Joshua, who asks Riku if he came through a Portal. Joshua explains that the world is split in half and that one can use a Portal to pass between the different versions of Traverse Town, and he asks Riku to find Rhyme, who is the key to the Portal.

Sora and Rhyme encounter Neku on a rooftop in the Fifth District, and Sora asks him if Rhyme is his game partner. Rhyme suddenly disappears, and the mysterious youth appears and summons the Hockomonkey. After defeating it, Sora and his friends are temporarily able to see events occurring in the other Traverse Town, and a Portal materializes, through which Joshua and Rhyme appear. Joshua explains that Traverse Town is split in two, and that Rhyme's dreams are his Portal, which allow him to travel between the two towns.

After defeating Ansem in the World That Never Was, Riku returns to the real world through a Portal. This Portal can also be used to return to the World Map of Riku's side.

After Riku and the others save Sora and return to the Mysterious Tower, Riku opens a Portal to enter Sora's heart and wake him from his sleep.

Link Portals
Link Portals are a type of portal that can be found in all Sleeping Worlds. They give special challenges for the protagonists, Rare Nightmares to battle, other Spirit's party or even allow them to battle stronger versions of the bosses, rewarding the player with Droplets, Dream Pieces, and other prizes if they are completed. Each portal belongs to a "player", usually named from a Final Fantasy character, like Auron, for example.

Mechanics
After the first few drops, Link Portals begin appearing throughout the worlds. They are displayed as pink dots in the lower Touch Screen, but they can't be seen in the top screen. When the player moves near the point where the portal is located, a small sign with the name of the owner, the difficulty rank, represented by five stars, and a symbol of the type of challenge or the Spirit Party of the portal will appear in the Touch Screen. If the player touches that sign, more details about the Link Portal will appear in the top screen. After reading the details, the player can decide to open or not the Link Portal.

There are four different types of Link Portals:
 * Battle Portals: These portals give the player a series of Nightmares to battle, according to another "player" Spirits. It also gives a "Bonus Objective" to be accomplished during the battle like defeating all Nightmares in a set time limit or doing a number of Flowmotion attacks. After opening the battle Portal, the word "start" will appear. After clearing the portal, either accomplishing the bonus objective or not, the word "finish" will appear, followed by the results of the portal, telling the player what was obtained. The player receive extra Drop Points and one of several prizes, like a Dream Piece. If the Bonus Objective was achieved, one of various possible bonus prizes will also be received.


 * Friendship Portals: These portals allow the player to temporarily borrow another player's Spirits. If this portal is activated, the player Spirits will be temporarily exchanged for the Friendship Portal Spirits, which come with the Link Gauge full and the HP gauge replaced by a time gauge divided in four segments that deplete over time. When that gauge runs out, the Spirits are exchanged with the player's Spirits again.


 * Special Portals: These portals pits the player against Rare Nightmares and give even better prizes, like Dream Eater recipes. There are six Special Portals for each character in each world, with the exception of The World That Never Was, that has only three. Only one will be open in any given world per drop. After all are beaten with one character, that character will receive the End of Pain Keychain.


 * Secret Portals: These portals are unlocked after beating the game. In them, the player can battle stronger versions of the bosses of the world they are in. After all are beaten with one character, that character will receive the Unbound Keychain.