The Omniverse

The Omniverse is the collection of every single universe, multiverse, megaverse, dimension (alternate or pocket) and realm.

Structure
Each plane a planeswalker travels to is a universe in and of itself. For the sake of clarity the term universe will be used to describe a collection of planes.

A single universe encompasses it's own version of each outer and inner plane. Thus the universe of Pharos has it's own Haven, Hell, Elemental Plane of Water, Positive Energy Plane, First World, etc. That said the Plane Shift and Gate spell only take you to that universes respective inner and outer planes.

Pharos
The source of The Beacon, and current main setting for Blind Eternities.