Role in Stargate Atlantis
Ronon is a native of Sateda, a planet with an advanced level of technology. His grandfather suffered from Second Childhood, a condition with symptoms similar to Alzheimer's Disease. Ronon became a member of the Satedan military where he held the rank of Specialist. He was very close to a woman named Melena, whom Ronon considered "close enough" to a wife in "Sunday". Approximately seven years before Ronon's first contact with the Atlantis Expedition, the Wraith attacked Sateda. Ronon remained behind with Melena to fight the Wraith, but the Wraith defeated Satedan forces and Melena was killed before Ronon's eyes in an explosion. Ronon was later captured by the Wraith. When the Wraith discovered that he is different than the normal human on Sateda (or any other human civilisation) - i.e. much stronger and more resilient - they turned him into a Runner, implanting a tracking device in his upper back and setting him loose to be constantly hunted. (for sports, training etc. as Ronon said later to Teyla).
Ronon stayed alive for seven years by learning several new tricks and deciding to hunt them back with his weapons. He owns a unique energy pistol which emits red bursts of energy that stun or kill at the user's discretion. It resembles a revolver with a power cell where the ammunition cylinder would be located. (The same type of weapon is shown to be used by a people in the season 4 episode "Travelers", but Ronon displays no knowledge of these people.) Ronon also carries a sword; the hilt is made from a Wraith mandible and humerus wrapped in Wraith hair, the blade is made from the metal of a Wraith ship, and the scabbard is made from a Wraith leather coat. The episode "The Hive" shows Ronon carrying several knives hidden on his person for use in emergencies. (He uses four in the episode and it is implied there may be more.) Ronon's seemingly unlimited supply of these blades is a source of occasional comic relief.
When the Atlantis team encounters Ronon for the first time in season 2's "Runner", they arrange a removal of the tracking device in his back. Ronon returns with them to Atlantis, where he learns that Sateda had been completely destroyed. Sheppard offers Ronon a place on his team in "Duet" after Ronon proves his worth against the Marines and Teyla in hand-to-hand combat and demonstrates his experience with guns. Ronon finds out in "Trinity" that about 300 Satedans survived the Wraith attacks and moved to other planets. In season 3's "Sateda", Ronon gets revenge on the Wraith who originally turned him into a Runner. Ronon meets with three of his old Satedan friends in season 4's "Reunion" and seriously considers leaving the Atlantis Expedition for the first time until he learns that his old friends are Wraith Worshippers. In the end, Ronon remains with the Atlantis Expedition, stating that his friends are "right here".
In season 4's "Midway", Teal'c comes to Atlantis to advise Ronon how to deal with the IOA. This immediately provokes a rivalry, and Ronon and Teal'c engage in a sparring match. After an hour of intense but inconclusive fighting, it is proven they are equally matched. Together, they fight a group of Wraith who attempt to gate to Earth; in the process, Dex saves Teal'c from a Wraith who is feeding on him and earns IOA approval of his presence at Atlantis. (The rivalry as such is resolved; the question of who could beat whom is left open, but they become friends instead of rivals.) In one episode of season 4, Ronon and Dr. Jennifer Keller appear to take a romantic interest in each other. In Season 5 episodes "Taken," "First Contact," and "The Lost Tribe," their potential attraction is again suggested until Dr. Keller reveals that she is interested in Dr. Rodney McKay. In season 5's final episode, "Enemy at the Gate", Ronon is killed during an assault on a Wraith hive that had reached Earth's orbit. He is then revived by a Wraith and interrogated, only to be rescued by Sheppard and crew. Dex is last seen with the Atlantis Expedition crew as they safely land a cloaked but disabled Atlantis near the Golden Gate Bridge.