The Link System (リンクシステム, Rinku Shisutemu?) is a game mechanic that appears in Kingdom Hearts 3D: Dream Drop Distance. It allows Sora and Riku to harness the powers of the Spirit Dream Eaters in their party.
Linking with a Spirit uses up the Link Gauge, which appears below its profile sprite. If one Spirit's Link Gauge is full, a Single Link can be initiated with it, and when both active Spirits have full Link Gauges, a Dual Link can be initiated with both of them. While a link is in effect, the Link Gauge or Gauges will steadily deplete until empty, although links can be ended or interrupted prematurely. The Link Gauge is filled when active Spirits attack enemies, or a Dream Candy is used.
Sora and Riku each use a different type of link with the Dream Eaters in their party.
Sora can join with a Spirit to execute a Link Attack (リンクアタック, Rinku Atakku?), a special technique utilizing the Spirit's natural abilities. Many species of Dream Eater have unique Link Actions associated with them, although some techniques are shared between species.
If there are two Dream Eaters in the party with full Link Gauges, Sora can initiate a Dual Attack. In most cases, the Dual Attack used is determined by the Attributes of the two Spirits.
Riku can fuse with a Spirit to initiate a Link Style (リンクスタイル, Rinku Sutairu?), which enhances his attack combos, similar to Command Styles from Kingdom Hearts Birth by Sleep. The Link Style used depends on the Style attribute of the fused Dream Eater.
If there are two Dream Eaters in the party with full Link Gauges, Riku can activate a Dual Style. The Dual Style used is determined by the Style attributes of the two Spirits.