From Dragon Ball Encyclopedia
The Evil Dragons (邪悪な 龍, Jaakuna Ryū; FUNimation "Shadow Dragons"; Literally meaning "Evil Dragon") are the evil beings created by the overuse of the Dragon Balls over the duration of the series, and were the final antagonists of the Dragon Ball metaseries. The fight against the Evil Dragons makes up the events of the Shadow Dragon Saga. The battle against the Evil Dragons can be considered the closing segment of the series (finding the Dragon Balls was the beginning) that teaches the Earthlings to stop relying on the Dragon Balls to solve their problems and can be seen as a metaphor for where the Dragon Balls finally turn against the Z Warriors. The Evil Dragons are (in order of appearance): Black Smoke Shen Long, Haze Shen Long, Rage Shen Long, Oceanus Shen Long, Naturon Shen Long, Nuova Shen Long, Eis Shen Long, and Syn Shen Long – who later becomes Omega Shen Long after absorbing the other six Evil Dragons' Dragon Balls. They are eventually all defeated by Son Goku except Nouva Shen Long, who was killed by Omega Shen Long. Of the seven, only Nuova, Eis, and Syn Shen Long have martial arts skills which pose a serious challenge to Goku. Nuova Shen Long is believed to have the least Negative Energy of the Evil Dragons due to his morals and the wish that created him. While most of the other Evil Dragons were made by very selfless wishes (or in the case of Oceanus, a wish that can be seen to be in a gray area), Nuova is created by a very selfish wish made by Piccolo Daimao, who wished for his youth and power to be restored.
Wishes and personalities
All of the Evil Dragons' personalities were inversely proportional to those of the wishes that created them (whether they were selfish or selfless). They also bore a direct relation to their time in the manga (comical or dark). Their battle powers were also directly proportional to the strength of the wishes used to give them life.
Haze Shen Long was the most comical of the Evil Dragons, created by a wish that took place during the the early half of the Fortuneteller Baba Saga – a very comical part of the anime in and of itself. The wish that created him revived only one person (Bora), and so the wish used relatively little power and lead to Haze being the weakest of the Evil Dragons.
Rage Shen Long was one of the deadliest Evil Dragons, created by the wish that revived Goku after he sacrificed himself to kill Raditz (only one person was affected directly, but it was designed to save everyone from the Saiyans). Rage Shen Long's power of Elasticity was strong enough to withstand Goku's 10x Kamehameha even though his offensive power was not even enough to hurt Super Saiyan 4 Goku at all. Rage was relatively dark compared to Haze or Oceanus, but was created in Dragon Ball Z, considered a much darker anime than Dragon Ball. He was also the only Evil Dragon to be defeated out of pure natural causes and not with any people involved (although the finishing blow was delivered by Goku). He would have won if it had not rained on him and caused his large body to short-circuit and diminish his power.
Oceanus Shen Long was the second most comical dragon, created in a time when the series was still very comical (specifically, the Emperor Pilaf Saga). She was both good (in that she provided free Fish to the townfolk, and it was only the townsfolk, not Oceanus, who abused their new-found laziness, although she may have counted on this) and bad (in that she used several dirty tactics to try and defeat Goku and polluted the town with rotten Fish), created by a wish which was neither completely good nor completely evil. Oolong wished for a hot girls' panties, or the most comfortable underwear in the world in the dubbed version. (Oolong's purpose for making the quick wish was to save the world from Pilaf, but the content of the wish was rather perverse).
Naturon Shen Long was the darkest of the first four Evil Dragons, created in a very dark time in Dragon Ball Z. He used very evil tactics (such as using Pan as a Human shield) mirroring the selfless wish to revive Majin Vegeta's victims in the Majin Buu Saga.
Nuova Shen Long was created by Piccolo Daimao's wish for eternal youth, which was undeniably selfish, and as such was the most noble and honorable of the Evil Dragons. He was very serious, as the King Piccolo Saga was a very dark and serious time in the Dragon Ball anime.
Eis Shen Long was among the dirtiest of all the Evil Dragons (he used both Pan and Nouva as shields to protect himself), created by a wish that was made so that, of all people, a mass murdering creature initially made to destroy everything could get a second chance, arguably making it the most selfless wish made.
Syn Shen Long was created by the wish that most likely revived the most victims since one can only reasonably assume that others besides the Namekians were killed by Freeza and his henchmen in the preceding year. Therefore, just as Haze (being created by a single person's revival) was the weakest, Syn (created by the most people's revival) was the strongest. Going further, just as this wish canceled out damages from Freeza's Force, the most terrible and feared force in the universe for a long time, Syn would absorb all of the Dragon Balls and achieve a form powerful enough for his Negative Energy to potentially rot away the entire universe - the entire universe which, before this could happen, provided the energy for the Genki Dama that was used to defeat him.
Their names in the English dub are related to the name "Shenron". When the dragons are ordered by ascending number of Dragon Ball stars, the first letter of their names spells SHENRON. These are their names, listed from 1 star to 7 star: