Oberyn Martell arrived in season 4 and took Kings Landing by storm. At least for the Game of Thrones audience.
Oberyn Martell’s star burned brightly, but was quickly snuffed out by the Mountain when he stood for Tyrion in the trial by combat.
Over the course of eight episodes, Oberyn Martell quickly became a fan favorite on Game of Thrones for his attitude, his refusal to abide by court norms and, let’s be honest, his open disdain for the Lannisters. It was the first time that Tywin had really encountered a character who he couldn’t pull rank on, and who was willing to openly challenge him. Tywin may have been hand of the King (and really King Reagent,) but Oberyn was a Prince, and his kingdom (Dorne) was never conquered by the Iron Throne.
Oberyn arrived in King’s Lending ostensibly for Joffrey’s wedding, but also to seek vengeance for his sister. That was his downfall.
Oberyn’s sister, Elia of Dorne, was Rhaegar Targaryen’s wife during Robert’s Rebellion. When Tywin Lannister and his army took King’s Landing Elia was one of the victims. But it wasn’t clean. the Mountain killed both her children (Aegon and Rhaenys) in front of her, brutally raped her and then murdered her. Because he was one of Tywin’s men, the Martell family never got justice for Elia, and the Lannisters never even acknowledged the Mountain was guilty of had done anything wrong. His mauling of Elia was essentially an open secret from the Rebellion up until the confrontation with Oberyn.
Oberyn got the nickname ‘The Red Viper’ largely because of his tendency to use poisons. And he made use of them during his fight with the Mountain. Oberyn got the Mountain down but then got a bit cocky. He had spent the entire fight trying to rip a confession from the Mountain about what he had done to Elia. It was like a dirge: “You raped her, you murdered her, you killed her children.” And “Say her name!” The episode of Game of Thrones actually toned down Oberyn’s delivery quite a bit.
Oberyn only faltered when he thought the Mountain might die before confessing. Then he backed off just enough that The Mountain was able to grab him, pull him down, and smash his head like an orange. It sounds gross and it was gross. Had Oberyn kept ahold of his emotions many things would be different. Tyrion might still be in King’s Landing, having been acquitted of Joffrey’s murder, so he wouldn’t have joined Daenerys. The mess that was the Dorne season 5 storyline might not have happened either.
Now Oberyn may be gone from the show, but his work will (hopefully) be finished when Game of Thrones returns for its final season on April 24.