Extinction
The High Dwarves of yore, having finished their duties and formed the world into what it would be today by both giving it shape, creating millions of races and plants and animals and defined the very building blocks of reality, martyred their lives and went into Eternal Slumber.
An event spoken of only in the oldest and greatest of Dwarven Tales, it is said that in the days when the world was still young, when the High Dwarves walked the lands carving and sculpting the landscape and seeding it with life as the great creator species, they soon saw their mission complete, as Dwulvor the Deathless sculpted and created the Dwarves of Modern day who inhabit the world below the earth, carving out their original home beneath mountains in titanic sprawling cave systems and underground cities. His duties done, Dwulvor the Deathless and his High Dwarven kin went into Eternal Slumber, their duties done.