Here is a glossary of people, places and things from the world of Tarn.

Al'Kazael — A world in the cosmic sea which collided with Tarn during the Worldrending. It is also called Witherdark. Little is known about this place, other than that it was ruled by a race of divines called the Vorgar. Some of these Vorgar, led by Maligor the Archfiend, entered Tarn and attempted to establish rulership of it during the Godstrife Era.

Avalar — A race of divines led by Ereus, whom came to power in the Avalarian Age. They resemble men and women of great stature, and excel in warfare, craftsmanship and architecture. After the ascension of Ereus, which marked the beginning of the Avalarian Age, some of the Avalar were given dominion over the elements. Avalar are the creators of men and dwarves, and are revered by these races.

Cosmic Sea — A vast sea of worlds which drift endlessly in the Void.

Crown of Heaven — A celestial realm located at the apex of the sky. Here Ereus is said to dwell with his Valkyries in mansions of stone atop the clouds.

Ereus — The foremost of the Avalar who rules in halls of stone at the Crown of Heaven. He is also called the Skyfather, Lord of the Skies, and the Wind King. Ereus takes the shape of a man, white of hair and beard with fierce blue eyes.

God Before Gods — A divine being whom is believed by his followers to be the creator of all worlds, and of all forms of life including the other divines. Some worshipers of the God Before Gods revere him alongside the other divines, such as the Avalar. But most sects by the time of the Dominion Era assert that all other divines are false gods, and should be viewed with contempt. This has led to strife between followers of the God Before Gods and people of other faiths, particularly those who worship Ereus. 

Tarn — The world in which Dragonvault takes place. It is not a planet by our modern perception, but an enclosed system, like a snow-globe, with a domed sky insulating it from the Cosmic Sea where all worlds drift. Atop the sky is the Crown of Heaven, and it looks down upon the Upperworld, where men dwell. Beneath the earth is the Underworld. The Netherworld lies much further below, near the Roots of the Earth, which stretch like tendrils into the cosmos.
Underworld — A deep subterranean realm which is roughly equal in size to the Upperworld. It can be accessed by caves or underground seas. It is lit by phosphorescent fauna, as well as a

Upperworld — The outermost realms of Tarn which stretch beneath the open sky. This place is sometimes called Midworld, for it lies below the realm of the gods, but above the Underworld. 

Valkyrie — A divine messenger of Ereus, resembling a beautiful winged woman clad in armor and bearing arms. They are said to dwell with Ereus in his celestial halls near the Crown of Heaven.