Positive Energy Plane
From Syra D&D Wiki
The Positive Energy Plane, formerly one of the Inner Planes, is a radiant place of infinite creation and endless light. Despite this, however, it extremely dangerous to visit: non-native beings who find themselves here will eventually absorb so much positive energy that they will explode in a burst of radiant energy.
It is unknown what has happened to the Positive Energy Plane in the wake of the Deity War. It is believed that it did not collapse into the Elemental Chaos like the elemental planes, yet all attempts to reach it magically have failed.