The Inner Worldlock

Long ago, when the Five roamed the plane, The Outer Planes had already been locked in place, with the Prime Material severed from the Astral Plane. The only method to reach the Outer Planes or the Astral Plane was through the Inner Planes, which were still free to move.
The Third Nelarian War  , however, was sparked with The Great Flood , when a group of Nelarian mages took advantage of a local nexus event, wherein the Elemental Plane of Water passed particularly close to the Central Rift Valley, and opened a Floodgate to the Elemental Plane of Water in the bottom of the valley, resulting in a massive flood and the deaths of millions of people. After the war was finished, the Five took it upon themselves to lock the Inner Planes in place, resulting in the formation of the Seven Nexii.
The results of the Inner and Outer Worldlocks is that the Prime Material is almost never visited by outsiders of any type, though Elementals are more common, as the Inner Planes are still connected to the Prime Material through the Ethereal Plane.

Manifestation

The Inner Worldlock results in the formation of the Seven Nexii, locations in the Prime Material where the Seven of the Elemental or Energy planes pass particularly close to the Prime Material itself.

Localization

The Nexii are located in seven very specific locations on the continent of Kaelat.

Type

Metaphysical, Elemental