Abyssal Binding Chain
Legend has it that the world of Arinthar was not always stuck in dangerous proximity to the Abyss, it roamed the celestial planes in a wider elliptic than most material worlds. The world at that time was known as Hai’Valen, and it was populated by ancient dragons of great power. The world’s erratic and interesting travels was what originally drew the dragons to settle on it.
But dark forces were hungrily watching the world’s path, and predicted its eventual arc through the edge of the lower regions. Five great chains of astral force were forged and hooked to Hai’Valen to form a stepping stone for the hordes of the Abyss to assault the upper regions.