Abyss is one of the twin realms, and is the magical counterpart to Exig. It was originally identical, however the presence of magic greatly altered the course of evolution as well as many other factors. For example, sentient beings evolved much earlier. Abyss is physically the same size as Exig, and its features are often similar. Since the King left, Abyss has been in a perpetual twilight.
Abyss overlaps Exig, existing in the same space and time, but with an invulnerable barrier often called the 'Veil' separating the worlds. Shards and Nobles can push through this barrier, but cannot pierce it. This is called 'Fade-walking'.
At one point, Abyss had an Abyssian King, but he left mysteriously over 15,000 years ago. This caused chaos for millenia, and Abyss hasn't been united since. Most abyssians refuse to crown one of the princes King, seemingly against their nature, and the princes decided to 'unite' them by force.