Dark Interlopers

The Dark Interlopers were a tribe of sorcerers, who in ancient times, had sought to attempt to control the Sacred Realm and ultimately the Triforce using a powerful relic called the Fused Shadow. In response to such audacity, the Goddesses of Hyrule ordered the three Light Spirits, Faron, Eldin, and Lanayru to seal up the power they had mastered, thus rendering the interlopers powerless. Fearing the goddesses, they were chased from Hyrule to the Gerudo Desert where they were eventually banished by the Goddesses of Hyrule, presumably by the Mirror of Twilight. This tribe would eventually become the Twili race due to their adaptations to the realm's light. They were mentioned to Link by the Spirit of Light Lanayru, who spoke of the dangers of wielding the Fused Shadow in Twilight Princess.

Backstory
In the cutscene following the revival of Lanayru, Dark Link seems to play a role as the Dark Interlopers:

At the start of the scene, Lanayru induces Link to have a vision that begins with a short version of the Deku Tree's telling of the creation of Hyrule, the Sacred Realm, and the Triforce. Link, clad in his starting Ordon garb, is first seen floating as a witness to the vision, then he and Ilia are seen as part of it, representing all peoples of Hyrule who lived in the prosperity given by the Triforce. But, the scene and music grow ominous, as Ilia is shown holding a serpentine, curved-bladed dagger, while Lanayru speaks of the first wars ever held in the name of entering the Sacred Realm and claiming the Triforce. As the view pans up to her blank-eyed gaze, she turns as if to strike Link beside her, but it seems that the now blank-eyed Link was quicker, and had stabbed her in her throat with the Ordon Sword.

After his victorious 'battle', Link plunges the sword into the ground. Now in his iconic green tunic, he is then seen running, dreamlike, towards the Triforce, which sits upon a small, grassy hill representing the Sacred Realm, but is stopped by three Dark Links who rise from the ground before the Triforce; the Dark Interlopers. Lanayru describes them as a tribe of Hyrule with powerful magic, who desired control of the Sacred Realm. The Interlopers summon the power of the complete Fused Shadow, which rises like a giant from the horizon, even eclipsing the Triforce itself. They then use their magic to completely vaporize Link (whose eyes are normal at this moment). The vision cuts and pans to show that the Dark Link in the middle has stolen Link's appearance (his coloration, at any rate), save for the eyes, which are blank again. He chuckles in triumph as a version of Ganon's main theme is heard, as if a theme song to the Interlopers themselves.

It was at that moment that Faron, Eldin, and Lanayru descended onto the scene and sealed the Interloper's powers, driving the Fused Shadow back down (with the Triforce nowhere to be seen), as the Interlopers turn in disbelief. The green-clad Dark Link then screams in terror, as all of the Interlopers are removed from the existence in the Light World, with a sudden, haunting finality. Lanayru reminds Link that the Fused Shadow is the artifact he has been reassembling, and warns Link of it's nature, and the corrupt nature of Power itself, as the vision shows a 'downpour' of slowly spinning, falling, madly laughing Ilias; an infectious madness that seems to touch Link himself. As the vision ends, Link awakens with a start, a look of shock upon his face.

Other Information

 * This form of Dark Link is also seen in Super Smash Bros. Brawl as playable costumes for Link and Toon Link.
 * This is one of the few (if not the only) monologues/narrations in the entire franchise, where the cutscene is not just a visual provided for the player while an NPC provides background, but an actual vision being experienced by Link himself.


 * It is possible that the Dark Interlopers could very well be the Gerudo from Ocarina of Time due to the mention of sorcerers as well as the latter Twili race having red hair. It is also possible that the Interlopers were Sheikah. They may even be the Ancient Tribe mentioned in The Legend of Zelda: Majora's Mask, who created the titular mask (which bears some resemblance to the Fused Shadow).
 * Most probably, the blank-eyed look of Ilia and Link are related to Lanayru's words, as it is he who is 'casting' the hallucination, as well as narrating: "Those who do not know the danger of wielding power will, before long, be ruled by it."