When a being first comes to possess a Divinity Shard, they are given a choice: Bear the Mantle of Divinity and ascend to Godhood, or refuse it and remain a lesser deity. Those who choose to bear the Mantle become a divine being, capable of being worshiped.

As a God they become the figurehead of an area of mortal concern, such as the concept of justice, the field of agriculture, the mastery of magic, the cycle of night and day, etc. It is not that a god has ultimate dominion or control over those concerns, but that they merely embody or represent them.

Deity is the term a supremely powerful being with all the powers of a Shard, but refuses to bear the Mantle. They may still have worshipers, but don't often embody a domain or bestow their grace upon mortals.

When the Archons vanished, their Divine Crystals were found shattered, scattered throughout the Realmwork.