King Orrin of Surda was a member of the House of Langfeld. The son of Larkin, he was a descendant of Lady Marelda of Langfeld and of Thanebrand the Ring-giver. He and his house were long-time allies of the Varden.
While indeed a brilliant man, he was a naïve and careless ruler, more concerned with his experiments than the affairs of his kingdom. Although ardent in his opposition to the Broddring Empire, Orrin felt that his scientific discoveries were just as important, if not more so, than the destruction of the Broddring Empire. Orrin is also shown to become a heavy drinker in Inheritance.
His scientific achievements included his proof for the existence of vacuum and his invention of the mercury barometer.
Relationship with the Varden
Though good friends with Nasuada, the two leaders had drastically different personalities and leadership styles.
At first, Orrin refused to have any relationship with the Varden and wanted to stay out of any conflict. But after the Battle under Farthen Dûr he allowed the Varden to come to Surda. Even after he decided war was necessary, he had a terrible time convincing anti-war aristocrats and organizations, like the Silk Guild, to join the cause.
Orrin objected to Nasuada not counseling with him more closely, such as meeting with Eragon's Elf-guards without informing him first and taking commands that had previously been his. He was annoyed at not receiving a full accounting of Eragon's actions at Helgrind, but was satisfied upon receiving a full explanation, as he felt that Eragon would not have been right had he chosen to execute Sloan, as one of the Undying should not take kingly power.
Due to his drastic change of character and increase in maturity throughout the Inheritance cycle, Nasuada often considered marrying him, but did not do so because she did not have any romantic feelings for him.
Life during the rider wars
Despite his former peace-loving policy, Orrin fought bravely at the Second Battle of The Burning Plains. He led his cavalry into battle personally, becoming not only a respected king but a national hero. He was also clever enough to allow Nasuada to be the overall commander over himself. He also fought (at great risk to himself) against the Laughing Dead when the Varden and many Urgal Rams were killed. He described the battle as "madness, worse than the Burning Plains,". He found that the "Ghoul" men could be killed by chopping their heads off.
Orrin also participated in the battles fought in Feinster, Belatona, Dras-Leona and Urû'baen. After the Rider War, he attempted to become King of the Broddring Empire, but was defeated in his bid by Nasuada, who instead became the Broddring Empire's leader, as well as making Orrin swear fealty to her. While Orrin initially disagreed with the idea of Nasuada becoming High Queen over the humans in Alagaësia, he was placated after Nasuada granted the country of Surda the lands and cities south of Belatona. However, the stress of the war had transformed him into a very heavy drinker, often able to finish a whole wine bottle alone in a single sitting, much to the annoyance of other members of the Varden.
Though he was not in any film, Orrin was described as not unpleasant to look at. His nose was high and thin though his jaw was strong and his mouth was finely carved and expressive. And he has a pleasing build because of all his martial training.
Both the scientific accomplishments Orrin shows Nasuada are based on those of the real-life scientist Evangelista Torricelli, who accomplished these experiments in the same way in real life.