Thunder Dragons are the masters of electricity. Their wings gather energy as they soar through the clouds, and when they clap their wings together they can create devastating arcs of lightning. They can stay airborne nearly indefinitely, landing only to sleep and breed; they catch their prey from the air and take moisture from the clouds. A thunder dragon’s roar is considered to be an omen of misfortune.

Dragons are highly-intelligent reptilian creatures that—from a human perspective, at least—appear to live forever. Many different varieties of dragon exist, each with their own unique qualities, habitats, and behavior. Adolescence in dragons is usually marked by the growth of a hatchling’s wings, although not all breeds of dragons grow wings and some breeds have other traits that indicate the beginning of maturation. In Galsreim, dragons and humans coexist peacefully.

Named after the Roman God of Thunder, Jupiter has received the same epithet like his brother "Zeus" which is called "Ryuudensei" or "Dragon Electricity Star" in English.

Different from his brother, he prefers to spend his day in the sky, flying. He also prefers to be admired than to be close or attached to someone. He also wants to be loved than to love somebody. This makes him quite a selfish dragons who only cares about him reputation. He is also known for his bad temper. If he is upset, he just sends some lighting at the next village or next dragon he sees, regardless if it is their fault for his mood or not.