Byakuren is a great white serpent living in the depths of the Ceras Lake. She is a prideful creature and when her life feeding on the fish at the bottom of the lake was disturbed by the Imperial City Recapture Army lowering the water levels and making their home there, she would grow more and more irritated.
Furious, she slithered onto the dock of the castle, attacking the Prince. After being defeated in battle, it was learned that she did not want to leave Ceras Lake even though it had become inhabited by humans, and so the Prince offered to let her join the Recapture Army, which she accepted.
She can't actually understand human speech but is able to communicate with humans via Genoh and also through the use of Levi's serpent-like staff. Being a female creature, Byakuren considers Miroon and Flail as her rivals in love.
After the Sun Rune War, Byakuren returned to her life of living under Ceras Lake, now much more peaceful with Ceras Lake Castle returned to the depths of the lake. Genoh is said to visit her often.