His mother, Miarkiona the Black, and his father, Undlir the Blue, were both wild dragons. When Galbatorix began attacking the Riders, Undlir was slain by Formora the Forsworn and her dragon and his heart of hearts was stolen. His mother flew from the Beor Mountains where she was hiding to Vroengard, where she gave her only egg, the egg of Rorkin, to the Riders, who hid it in the Vault of Souls until it was retrieved by Eragon and Saphira, who brought it to Fells abr Shur'tugalar. There he was found as an egg by Dair during his stay at Fells abr Shur'tugalar, accidentally dropped when the eggs were being shown to the future Riders in an attempt to hatch them. When Dair decided to return it to Eragon, Rorkin deemed him worthy and chose to hatch for him. This occurence was able to bring Dair's father, Deniareh, out of depression.
He is still small compared to other dragons, but is very wiry and quick, his weakness being his lack of stamina in battle, allowing him to be easily defeated by foes who can evade his attacks and outlast him, usually being larger, older dragons. He has bright yellow eyes with unusually round pupils, as most dragons have slits rather than orbs for pupils. The spines along his back and on his head lighter than his scales, but only slightly so. He often hunts by the cover of night, due to his dark scales, and sleeps in, contrary to his rider Dair, who rises early every morning from habit.
Despite what most expect his personality to be like, he is very polite, and never turns down a visitor. Like his Rider, he has a good sense of humor and is generally kind, but has a short temper and tends to go on destructive rampages while in a fight. He is also extremely naive, and feels everybody has good intentions unless he is proven wrong, which exasperated his Rider greatly. Even though he is still young, he has shown wisdom far beyond his age, like most dragons. Despite his wisdom and how naive he is, he isn't entirely trustworthy of dwarves unless they've proven themselves friends, as they attacked his mother while she was in the Beor Mountains, hiding from Galbatorix and the Forsworn, albeit they had a good cause, as she was attacking a herd of Nagra a group of dwarves were breeding. He also despises pigs, saying they're too small to make him feel full and they're obnoxious, though he will eat them if he has to or if they're given to him. On the contrast, he has a large amount of respect for the hearts of hearts from the Vault of Souls, as they watched over his egg for over a century, especially Valdr, with whom he had multiple conversations after his hatching.
Despite being opposites in many ways, they manage get get along very well better than many other dragons and Riders. Rorkin and Dair have never been apart since Rorkin first hatched, aside from classes at Fells abr Shur'tugalar, so they've become very attached to each other and are usually found doing things together, from reading (Rorkin managed to learn from Dair and other Riders, but is still slow and mispronounces many words) to strategy games to aerial tricks.