Dimension Link

The Dimension Link, also known as D-Link, is a feature of summoning in Kingdom Hearts Birth by Sleep. Its name connects to its purpose as a link to summon a character's power from another world.

The player is also able to D-Link their friends while using their wireless functions. They appear as Terra, Aqua and Ven in their armor. It is unknown if a character can summon their own armored form.

Usage
To use the D-Link system, you must add the it as a D-Link Command into your separate D-Link menu and can only use it when your D-Link (or Dimension Link) gauge is full. The D-Link gauge is blue and next to the HP meter. You fill up your D-Link gauge by obtaining dropped blue prizes from enemies like obtaining Drive Orbs to fill your Drive Gauge in Kingdom Hearts II.

Once you have linked with a character, it changes the Command Menu gauge that is also used for Mode Changes to show how long your companion stays on the field and the face of the companion you’ve linked to will show up on the bottom right of the screen. By linking to them you will get more powerful, and be able to use unique Finish moves which have two different power up levels which they perform after gaining certain symbols next to their character image on the right of the screen.

Terra

 * 1 Symbol: Gold Seal (From Terra's belt)
 * 2 Symbols: Shield

Ven
D-Link Used Commands:
 * 1 Symbol: Blue light resmembling wind
 * 2 Symbols: Green Keyblade

Final Break x2, Strike Raid, Slide Dash x2, Freeze Raid, Aerora, Cura

D-Link Effect:

Speed King, and Haste. Increase speed of normal attack.

Finish Command:

Finish, Speedy rapid combo attack.

Air dive, when using it, press O/X/Square/Triangle button to hit enemies from the air.

Aqua

 * 1 Symbol: Hidden Mickey Symbol
 * 2 Symbols: Green Crystal

Cinderella

 * 1 Symbol: Tiara
 * 2 Symbols: Glass Slippers

When you have 0-1 Symbols, you can activate “Dream Sparkle” which raises enemies up into the sky by a magic light. At 2 Symbols, you can activate “Dream Waltz”, where you will spin making a magic vortex. With either one, when you’re suppose to start the Finish move, the Carriage will appear. The Carriage will move towards the castle when you press the button at the right time.

Snow White
When you have 2 Symbols, You can execute "Colorful Diamonds", creating seven colored jewels surrounding you and sending them to attack nearby enemies. The commands available are mostly Magic based like, Sleep, Blackout, Mini, Curaga, and Aeroga.
 * 1 Symbol: Blue Bird
 * 2 Symbols: Rabbit

Experiment 626

 * 1 Symbol: Laser Gun
 * 2 Symbols: Spaceship

When you have 0 -1 Symbols, you can activate “Reflect Beam”. If you press the button that appears on the screen at the right time, a beam that can reflect objects will appear. When you have 2 Symbols you can activate “Ohana Beam”. Buttons will go from right to left, and if you’ve hit them all a sound wave will come from the a ukulele and attack your enemies. It seems you can use both at the same time. The Commands you can use are mostly Thunder-types. “Thunder Blitz”, “Stun Blade”, and “Esuna” are the first ones you get. Also, there are effects when you are in D-LINK, with 1 Symbol giving you an “Attack Up”, and 2 Symbols giving you “CP x 2”.

Mickey Mouse

 * 1 Symbol: Star Seeker Keyblade
 * 2 Symbols: Star Fragment

When you have 2 Symbols, you can execute "Holy Blast" where a Mickey head logo spins around in a circle and you must press the right button once it passes over a certain section of the circle. The attack "Holy" releases in bullets of light. The ability bears a similarity to Riku's Holy Burst Sleight from Kingdom Hearts Re:Chain of Memories.

Zack

 * 1 Symbol: Support (Blue) Materia
 * 2 Symbols: Summon (Red) Materia

When you have 2 Symbols, you can execute "Hero's Pride". You can borrow power from Zack and gain new abilities. It sends out a blast from the Keyblade.

Peter Pan

 * 1 Symbol: Red Feather
 * 2 Symbols: Dagger

Maleficent

 * 1 Symbol: Staff
 * 2 Symbols: Diablo

Donald Duck
When you have 2 Symbols, you can execute "Force Flare". As seen in Kingdom Hearts II, it is one of Donald's Limits with Sora.
 * 1 Symbol: Mage's Hat
 * 2 Symbols: Mage's Staff

Goofy

 * 1 Symbol: Knight's Helmet
 * 2 Symbols: Knight's Shield

Vanitas
This D-Link is only available in the last battle of Ventus´ story, when Vanitas destroys the pillar of Awakening. It allows you to fly (but not very often because Vanitas will be attacking you most of the time) and also gives you the necessary attacks to defeat Vanitas once and for all.

Wireless D-Links
Players also have the ability to connect with other players wirelessly and make them available for the D-Link system. You can link up with friends and set up a D-Link with their character and can use their character's abilities.

Terra

 * 1 Symbol:
 * 2 Symbols:

Ven

 * 1 Symbol:
 * 2 Symbols:

Aqua

 * 1 Symbol:
 * 2 Symbols: