The Nexus is the place where it all comes together. It is here that Chronos the Time Keeper with the machine Oracle tries to maintain the balance between the power of Order and Chaos in Oblivion. He feeds the powers of the Order realms and the Chaos realms to the respective goddess and god - Arella or Abaddon. Time stands still in the realms connected to the Nexus bar Mortalis, Mortalis appears not to be that connected to it for we still have the power of time, although Scree does mention that if Chaos takes full control, even Mortalis will be affected.
Each of these realms can be entered through the Nexus by passing through a courtyard which takes influence, architecturally from whichever realm you are about to step foot within.
Beyond the temple that the Oracle is situated within seems to be an endless cosmic cloud of colour and abrupt weather, it is uncertain if the realm often harbours scenery such as this, or if it is to do with Abaddon's ever tightening grip on chaos.