Chaos is utterly inhospitable to the inhabitants of Cosmos. It is envisioned as a nausating, roiling abyss, simultaneously crushingly massive and an infinite void. It is also known as Erebus or Pandemonium.
The latter name comes from the abundance of shrieking spirits and primordeal creatures found in Chaos, always nuzzling at Limbo, searching for a way in.
Chaos interfaces with Limbo and Tarterus.