From Zelda Legends Wiki
Dark Link (not to be confused with Shadow Link from Four Swords Adventures) is a recurring boss character who first appeared as the final boss in Zelda II: The Adventure of Link. In that game, Link earned the Triforce of Courage by defeating his own dark double. Dark Link is very erratic in his attack pattern, and difficult to hit. Dark Link next appeared in Ocarina of Time, this time as a sub-boss in the Water Temple. He was very similar to his appearance in Zelda II, but he had a few extra abilities including the ability to stand on Link's sword. However, he can't block Din's Fire. His most recent appearance was in the GBA version of A Link to the Past, where he was the boss of the Palace of the Four Sword, which could only be reached by beating both games on the Game Pak. He had multiple forms corresponding to the colors of the Links in Four Swords.