The Twilight Kingdom is the home of the Keep of Four Worlds. Located in the same shadow as the Maerturi's Vale of All, the kingdom is an ancient place. Abandoned millenia ago by the ancestors of the Maerturi, it plays a crucial role in the Maerturi prophesy.
The Maerturi ancestors were the protectors of the Font of Eternity, a breach in the structure of the universe where all four planes merge in a tumultuous flow of pure elemental power. This breach was created by the Serpent in the days after the Pole of Order was formed. It was his last cognizant act, a last desperate attempt to once again entrap the Unicorn before he fell completely into madness.. The ancient peoples of the Twilight used the power (at the cost of their own lives) to cap the breach, but could not contain it entirely. They were only able to block most of it. The remainder of the flow was channeled into a pool at the very center of a fortified keep. This became known as the Font of Eternity. And for their selfless acts on behalf of all the planes, (for the breach would surely have destroyed the new-born Pole of Order), and for what she knew would come, the Unicorn watches over them.
And while a majority of the breech's power was contained, what was left in the Font was enough to grant great power to those who bathed in or tasted its waters. Visions were granted, as well as abilities far beyond what anyone had known. Those who gave themselves over to the Font entirely, tapping the immense hidden potential were granted power beyond belief, power equivalent to that of the creator of the Universe himself. But it did not come without price. As the Great Artist had slowly lost himself to the power he was granted, so did those that gave themselves over to the Font. It was a power beyond any one individual's ability to contemplate or control, and it consumed the initiates soul. This is what happened to Brand, who discovered the Font during his travels. It, and the Twlilight Kingdom, exists simultaneously in all four Universes. And Unlike the Grove, or Ygg, it is the only place that one can access all four planes without having to use the Patterns. Living that near the essence of Reality made the Twilight peoples as real as those who live in Amber, near the Pattern.
And so for millenia the Twilight people guarded the Font, until the day, some two thousand years ago, that one of the Seekers, the vaunted prophets of the Twilight folk, who were the primary guards of the Font, tasted of its waters and gave forth a prophesy before she died.
And the time shall come when the battle shall come to the place between Light and Darkness, the battle to protect the place where no shadows fall. To protect Eternity, it must be abandoned now. For if shadows fall in the place where none have before then the breach shall be torn anew. To protect the Font, the battle of shadows and dust, fought on the wings of morning must be won, at the cost of our life, our blood and our souls.What the seeker saw was the Serpent reopening the breach, and using the full power of the Font to extinguish the Light utterly. She saw this happening after a great battle, in which the Amberites lost, outnumbered as they were against the horde of Darkness. She saw them ascend to the Tir in the twilight, and using those of The Blood, destroy the Pattern there, allowing them access to the Place where no Shadows Fall, the Unicorn's Realm. And once they had gained entry there, they made their way to the Twilight Kingdom, and ripped the veil of the worlds, and used the power of the Font to destroy the Unicorn and her realm.
We shall end for the Light from which we were born. And when the Silent Walker shall bring to us our savior, the Chosen shall lead us to the place where no shadows fall, shall lead us into the battle of shadows and dust, shall lead us to our end, and our beginning.
We become Maerturi.
And she knew that only with a great sacrifice, could that future be averted. The sacrifice of an entire people who had already devoted themselves to the Light.