The Abyssal Shard and formation of the Abyss

The Abyssal Shard arrived in the multiverse through its own magics from collapsing ancient universe, one never apart of this one. This Shard held the collective power of the dark race which had conquered and ruled this other multiverse, and sought a way to escape the inevitable collapse of their universe.

The Shard arrived into the possession of a Powerful Primordial. The evil within the shard attempted to convince him to place the shard within the Astral Sea, to allow it to consume the whole of existence, and remake it into a better world. It promised him power beyond all imagining.
The Primordial Tharzidun, grew greedy, and attempted to unlock the power of the Shard himself within the Elemental Chaos. This did not got as planned for him. Instead the Shard Erupted with its power, flowing through Tharzidun and the Elemental Chaos around him.
A vast vortex opened up, and from the Vortex emerged the Obyriths. Horrifying creatures, of dark power from another collapsing universe. The Shard consumed more and more of the Elemental Chaos, drawing in all the chaos. Primordials caught in its wake were deformed and turned into horrifying demonic creatures. Tharzidun, holding the Shard, become extreamly powerful. But the energy eminating from the vortex was drawn to the Negative Energy of the lower planes, near the planes of Hell. Consuming more and more of the chaos, the Vortex decended and left what was once the Elemental Chaos plane.
This left behind a elemental realm not quite, but almost void of the original Chaos that once ruled it. The Primordials that remained were delighted with their new realms, and the Elemental planes were created.
  The Whirlpool of power fell to the Lower planes, and nearly obliterated Carceri, forming the abyss, and ever expanding hole essentially, and Pandemonium, as its powers crept out into the surrounding planes. It also corrupted Carceri with a great feeling of Chaos.