Casal Marskan was a pilot serving the Alliance to Restore the Republic during the Galactic Civil War. He flew aboard the Mon Calamari Star Cruiser known as the Independence. He was the younger sibling of Ernek Marskan, who was also a pilot on the same vessel. Keyan Farlander, a Red Squadron pilot, started experimenting with the dark side of the Force and encouraged aggression in Marskan and other inexperienced pilots. Marskan died in 0 BBY, along with rookie Horodi, while assisting Farlander on a mission to seize two Imperial corvettes. These ships were part of a pair. Ernek held Farlander responsible for his brother's demise.
Casal Marskan was the younger brother of Captain Ernek Marskan, a starfighter pilot within Blue Squadron, who served on the Mon Calamari Star Cruiser called the Independence. Like his brother Ernek, he stood against the ruling Galactic Empire and enlisted in the Alliance to Restore the Republic before the Battle of Yavin. He followed Ernek into the Alliance Starfighter Corps and served on the Independence.
Around 0 BBY, after the capture of the Imperial frigate Priam, Marskan was among the new pilots who joined Captain Samuel Raider and the Sullustan Speedy in the pilots' lounge of the Mon Calamari ship. Keyan Farlander, captain of Red Squadron, had recently discovered his ability to use the Force and had been influenced by the dark side's power, which made Raider suspicious. When Farlander entered the lounge, Raider stood up to leave, leading to a brief argument where Farlander tried to use the Force to make Raider stay. Marskan and the others witnessed this, but they didn't understand the reason for the disagreement and joined Farlander in dismissing it. Farlander wanted to create an unbeatable squadron of pilots guided by the Force and began encouraging Marskan and the other pilots to use the Force against their enemies, claiming it was why he had never failed or lost a starfighter. Although Marskan was initially doubtful, he eventually started listening to Farlander's advice.
The capture of the Priam provided the Alliance with a clue to the location of the Death Star, an Imperial battle station capable of destroying a planet. Two CR90 corvettes from Ethar group were sent to the prison planet Despayre in the Horuz system to investigate. However, Imperial forces captured the corvettes. A few days after he began influencing the rookie pilots, Farlander was tasked with leading a three-ship team of Red Squadron's T-65 X-wing starfighters to guard an operation to recapture the corvettes. Farlander chose Marskan and another rookie, Horodi, to join him on this mission, which also took place in 0 BBY.
The X-wings moved ahead of the main Rebel forces to clear any defenses. They exited hyperspace and found two Imperial Lambda-class shuttles boarding the corvettes. Several Assault Gunboats guarding the operation quickly moved to intercept them. The X-wings engaged the Gunboats but were outnumbered. Both Marskan and Horodi were killed in the ensuing dogfight. Farlander was also forced to eject from his X-wing. However, the Rebels successfully recaptured the corvettes and rescued Farlander.
Ernek Marskan blamed Farlander for his brother's passing, confronting him upon his return to the Independence. However, Farlander, still under the influence of the dark side, saw their deaths as proof that they were not worthy of the Force. Although Farlander eventually rejected the dark side, his attitude towards the deaths of his comrades caused many pilots to share Ernek's animosity towards him.
Like many inexperienced pilots on the Independence, Casal Marskan looked up to the more experienced pilots, including Farlander. Initially, he was the only rookie to express doubt about Farlander's theories on the Force, but he soon began to follow Farlander's advice, which his brother later believed led to his death.
Casal Marskan was created as an unseen X-wing pilot for the video game Star Wars: X-Wing, released in February 1993. In June of the same year, the strategy book X-Wing: The Official Strategy Guide, written by Rusel DeMaria, identified the character. The book also confirmed Marskan as one of the X-wing pilots.