Chaos
Chaos is the force that plays anathema to Creation. It exists in its purest form in a vast realm outside of the known multiverse (not to be confused with the Chaos Plane, which is a part of the multiverse), a realm composed solely of this raw, primordial energy. When Ayar created Achaea, He did so in two parts. The first was orderly Creation, composed of the structured planes of existence that mortals are familiar with. The second was that of Chaos, which is its polar opposite. No one knows why this was done, though some scholars theorise that perhaps each realm's existence is dependent upon the other.
Beings from the realms of chaos include the Unnamable Horror, the Spawn of the Unnamable Horror, Entropy, and Discord. Though focusing largely on the Chaos Plane and not the realms of true chaos, many of the abilities that Occultists utilise centre around the forbidden knowledge and eldritch revelations of the realms and beings of chaos that untrained mortal minds are simply too fragile to accept.