With every new generation to the games, there comes at least one dragon type with a three stage evolutionary line. The fifth generation came out with two, the Axew and Deino lines. Deino, though, has dragon as its secondary type and has a unique type combination that no other Pokemon outside of its evolutionary line shares.
Deino is primarily a blue dinosaur-like creature with a sort of black hair/fur covering its neck, head, and most of its face. Its neck fur is speckled with magenta spots and it has a ragged, blue tail. Deino’s and Bagon’s evolutionary lines are the only Pokemon exclusively in the Dragon egg group. According to Ken Sugimori, the Deino line was originally intended to be made up of cyborg dragons – part tank and part dragon. The idea was scrapped until late in the game where the creators decided to base the line on the Yamata no Orochi (a serpent-like creature with many heads and tails). According to Deino’s pokedex entries, Deino tends to bite everything and isn’t much of a picky eater. They cannot see, so they tackle and bite to learn their surroundings. Because of this, their bodies are riddled with wounds. Approaching it carelessly is extremely dangerous. Its name seems to come from the words ‘dino’ (a shortened version of the word for “dinosaur”) and ‘ein’ – German for “one”.
Once Deino reaches level 50, it evolves into Zweilous. Zweilous shares many physical traits with its pre-evolution, though has two heads and a wider body. Zweilous, like Deino, has the same sort of black hair covering its neck, head, and most of its face, and is primarily colored blue. It has four legs and two appendages coming off from its back that appear to be wing-like. The red marks on its stomach seem to come from its original design from when it was supposed to be a cyborg-dragon, as they’re tire-mark shaped. Alphabetically, Zweilous is the last Pokemon listed. According to its pokedex entries, Zweilous’s two heads do not get along with each other. Because of this, they compete with each other for food and end up always eating too much. After Zweilous have eaten all of the food in their territory, they move to a new area. Zweilous’s name most-likely comes from the words ‘zwei’ (which means “two” in German) and ‘jealous’ – as the two heads are known to compete for food.
Finally, Zweilous evolves into its final form, Hydreigon, at level 64. Hydreigon is quite large, its legs, a portion of its stomach and each of its three faces are blue in coloration. The tip of its tail and its three necks are covered in the same black fur as its pre-evolutions and it has six black, matching appendages that are apparently wings. Its two smaller heads look as if they were meant to be arms as well. Hydreigon’s pokedex entries state that it is brutal and travels the sky with its six wings. Anything that moves seems like a foe to it, which provokes it to attack. They also state that the heads on its arms do not have brains. Hydreigon use their three heads to consume and destroy everything in its path. Hydreigon’s name is probably a combination of the words ‘hydra’ (a creature from ancient Greek mythology that would replace a cut-off head with two more to take its place), ‘drei’ (meaning “three” in German), and ‘dragon’.