Existing wholly within its own pocket dimension, there is no "mundane" way to reach the isle. It is eternally suspended in twilight: the dying rays of the setting sun light the western sky, and stars twinkle in the East. The isle is surrounded by mountains along all shores save the South, which boasts a beautiful lagoon with blue water and soft sands that contain the Portal through which you arrived. Rich fields and forests lie to the West, the tallest mountains touch the sky to the East, and a smoky volcano burns to the North.
Carved into the cooling lava, the Rings are a permanent feature of the landscape, and contain great magical power. These rings limit the spells that may be worked within. They also prevent any spells from crossing its boundaries, and heal all wounds as duelists exit. After all, these duels are not to the death.
Sometimes the trees around the ancient rings crackle with St. Elmo's Fire, becoming suddenly more alive. Encircled in blue, electric sparks, the aged trees snap and shiver, reaching toward the Magi with skeletal branches.
As you arrive, you are greeted by a goblin, who rushes up to offer a drink or a light meal (do you dare trust it?). Then a smile and nod from the official: "Welcome to Twilight Island! May magic and luck grace your path herein."