When Water Dragons mature, they lose the ability to survive on land, entering the water permanently. They are adept swimmers and eat whatever fish are in the lake they live in. They tend to inhabit the same lake for their entire lives, although a few live in the ocean and swim all over the world.

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.

On the great captain Aronnax's quest to find the sea monster, he came face to face with one big sea monster yet unnamed he pleaded the water dragon to give them some fruit for most of the team had scurvy, the nameless dragon said that he would let the expedition live if they said nothing about what they had seen. The captain promised and said: "It is a pitiful thing that such a brilliant creature like you should not have a name so I shall call you Aronnax's nightmare because of the way you will haunt my sleep forever."

And that is where his name comes from.