Vanitas is a Dimension Link for Ventus in Kingdom Hearts Birth by Sleep. Ventus obtains it once he reduces Vanitas to one HP during their battle in the Dive to the Heart, and must use its "Last Word" Finish Command to finish Vanitas off once and for all. The command gauge will only fill when Ventus wins a "clash" with Vanitas. Attacking regularly, as well as using one of the D-Link commands without Vanitas attempting to counter with the same one, will not charge the Command Guage. As it can only be used during this boss fight, it is impossible to level up.
The Vanitas D-Link enables fast, strong attacks using darkness, much like Vanitas's actual fighting style. It also changes Ventus's Shotlock Command to "Dark Link", and allows Ventus to hover in the void left in the Dive to the Heart when the Station was destroyed.
 Level 0
 Exclusive Commands
 Dark Spiral
In Dark Spiral (ダークスパイラル Dāku Supairaru ), the player charges forward at a fast pace, covered in light energy. If the enemy is hit, then the player can input two button presses to follow up with two more charges, similar to Sonic Blade and Chaos Blade.
When clashing with Vanitas while using Dark Spiral, the player can win the clash by quickly rotating the analog stick counter-clockwise.
 Dark Splicer
In Dark Splicer (ダークスプライサー Dāku Supuraisā ), the player teleports around the enemy multiple times, slashing at them, similar to Time Splicer without the stop effect. The player has a choice of continuing the attack by pressing the buttons prompted.
Vanitas rarely uses Dark Splicer himself, but if he does, countering with Dark Splicer will trigger a "slowed time" or "blurring" effect. If you input the commands properly, you will evade Vanitas's attacks and slash him away.
 Dark Link
Dark Link (ダークオブリンク Dāku obu Rinku , lit. "Dark of Link") is a light version of Vanitas' personal Shotlock, Dark Cannon. Three crystals appear in a trigram formation, and project rays that fuse and become a giant beam of light energy.
 Last Word
Last Word (ラストチャージ Rasuto Chāji , lit. "Last Charge") creates three beams of crystallized light around the opponent, followed by a powerful slash through the columns in the direction you are facing. Therefore, if you are not locked on, and not facing Vanitas, it is possible to miss with this attack.