warning: some spoilers
According to The Book Of Mena, before the time of Luminous Arc, Witches worked with Dragons to defeat the God Zehaal and did so by putting him in a deep sleep for many many years.
In the universe of Luminas Arc, there are only two living "dragons" that are known of. These are Alph and theo, who, while human contain the dragon heritage that allows them to access the ancient power of dragons, or ryms. The two become aware of and eventually are able to awaken their dragon/rym powers through the company and communication of the witches. Witches have a sugested history with dragons and know ryms to be fateful companions. The occasionally mentioned "fated kinship" between Lucia and Alph is example of this. Rym protect and use their powers to aid the witches. When Alph is "awakened" his priorities turn to protecting Lucia, and protecting the world from Zehaal.
"Fateful kinships"Alph is the only Rym to have connected with a witch during the time of Luminous Arc, as Vanessa has teased Theo on numerous accounts about becoming her Rym.
When Theo and Alph are fully "Awakened" and can access their dragon/rym abilities their battle classes change along with some skills. Theo is awakened before Alph, and his class changes from Archer to RymGuard. While he still uses a bow, and his archer skills are not changed, his Flash Drive abilities change to reflect his Rym status. Alph changes his class from Riffleman to Rym Hero after the second battle with the Steel Witch. His outfit, unlike Theo's changes. He still uses many riffleman skills, but gains three deffensive Rym Skills. His Flash Drive is also changed to reflect his Rym status.
Dragon/Rym as an element
Elemental effects are present in the game and paying attention to them can greatly aid in battle. Dragon/Rym is considered an element of its own, but is considered nuetral as an element in battle. This has its benefits, even in a game whose battle system considers elements.