Battle for the Sacred Realm

The Interloper War is a fanon name for the conflict that occurred in the backstory of The Legend of Zelda: Twilight Princess.

Summary
For a long time, the land of Hyrule lived in peace and prosperity after its creation by the Golden Goddesses; Din, Nayru, and Farore. After the goddesses were finished with Hyrule, they created another parallel world known as the Sacred Realm. Before departing the realm, the Golden Goddesses left behind the three golden triangles filled with their power, these three triangles when put together would become a larger triangle known as the Triforce.

The Triforce granted the wishes of those who touched it, and granted the one who touched it nearly limitless power. However, the goddesses wished to keep the power out of evil, and so if the one who touched the Triforce was unrighteous, the Triforce would split into three, leaving the one who touched it with the piece representing the force the one believed in most. The other two parts would be given to those destined, these two bearing the mark of the Triforce on their hands.

The legend spread across Hyrule, causing a great war over the location of the Sacred Realm. During this war, the tribe skilled in dark magic known only as the Dark Interlopers attempted to establish dominion over the Sacred Realm and establish their power using the Fused Shadow. This prompted the intervention of the Light Spirits which sealed the Interlopers in the Twilight Realm. They also sealed away the great magic those individuals had mastered, and splintered it, so it became the fragments of the Fused Shadow hidden in the temples of Hyrule.

The descendants of the Interlopers became the Twili, doomed to live as mere shadows in the Twilight.

It is unknown whether this is the same war as the Imprisoning War or the Hyrulean Civil War mentioned as the backstory for Ocarina of Time.