Rocky, a Houndoom who began as a Houndour, was the very first Pokémon of Ryan. Growing up in Johto, Ryan's Mother gave an infant Houndour, whom she named Rocky, to her infant son, Ryan, as a childhood companion. When Ryan was a mere 3 years of age, Rocky protected him from a wild Mightyena, causing him to cling more closely to Rocky in his later years of life. At the age of 10, after receiving a Cyndaquil from Professor Elm, Rocky challenged the new Pokémon to a battle out of jealousy, but lost.
Later that same night, it tried to run away, feeling abandoned by Ryan. Ryan, however, felt bad for making Rocky jealous and stopped it from running away, declaring the two to always be friends. He then challenged Rocky to a battle to prove himself as its friend and new trainer. Rocky again lost the battle, but was this time caught inside a Love Ball and joined Ryan on his Pokémon journey.
At the time of Ryan's promotion to Gym Leader of the Hora region, Rocky had evolved into a Houndoom.
Having the same coloration as its pre-evolved form, Houndour, Houndoom has a taller build with a longer snout. There are two white bands at each of Houndoom's ankles instead of just one, as well as three bands on its back instead of two. Houndoom has a long, skinny tail that ends in an arrowhead and visible claws on its feet. It appears to have a collar with a small skull pendant and a pair of curled horns, but no discernible ears.
Houndoom, especially Rocky, are generally very protective, alert, headstrong, intelligent, and very focused. It can be overly aggressive, but only to protect themselves, their young, their territory, or their owner. However, when properly trained, they can be extremely loyal, loving, and caring Pokémon, as well as very good pets. In a Houndoom pack, the Houndoom with its horns raked sharply towards the back serves a leadership role. Houndoom choose their leader by fighting amongst themselves.
Houndoom's abilities are the same as Houndour's, only stronger. As a matter of fact, legends claim that anyone that gets burned by Houndoom's Fire attacks will never be healed and that Houndoom's howling was once claimed to be the call of the Grim Reaper. Its fire comes from toxins burning in its gut, this also gives its fire a foul odor.