Eternity Crystals

The Eternity Crystals were referenced in the scholar's journal in the Temple Behind the Waterfall.

Summary

Once, the world was consumed by chaos. The Elemetal Planes flowed freely into the Material Plane. As they powerful elemental forces encountered each other, they broke and reshaped the world.
Then, as the First Epoch began, powerful beings began to tame the elemental powers, bending them to their will. They began to bring order to the Material Plane and control the flow of elemental energy, allowing the mortal races to develop and civilizations to rise. They sealed the Material Plane against the incursions from the Elemental Planes with eternal crystals.

Spread

The Eternity Crystals are occasionally referenced in colloquialisms that many no longer even consider the original meaning of, such as:

"Until the crystals crack..." meaning until the end of time

"...like finding an Eternity Crystal..." meaning to find something so rare it is obsurd and unlikey to actually be true or real

"...you'd break a crystal..." meaning one is careless or reckless enough to break an Eternity Crystal and send the world back into chaos.

Date of Setting

Before the first Epoch