A demo account is created by a Steam account that downloaded a demo version through Steam, or created using a Username/Password combination by a copy of the game obtained outside of Steam.
The only limitations of a demo account is that the quest "Trial of strength : Knight" cannot be accepted. This also means that any castle beyond "Desert storm" cannot be conquered. All PvE content and all maps are accessible however! No advantages are given to full accounts over demo accounts in regard to experience and combat abilities. A message with the demo status of the game will show up before every login.
Upgrading to full account
Purchasing the game through the Steam store page will upgrade all accounts linked to your Steam account automatically. After purchase, you will have to restart the game for the upgrade to happen. This will also remove the demo status message and all future accounts will be full accounts.
Upgrading an individual account will also happen when: - At least 2000 crystal is spent in game OR - At least 500 crystal is bought with out of game currency. This can only be accomplished on demo versions downloaded from Steam and linked to a Steam account. Upgrading an individual account will turn that account/identity into a full account. However, any other identities created from the main menu will still be demo accounts, and the demo status message will not be removed.