Mark James Langley is the commander of the Eta Squad, a faction of the Skylords that defected following the war against Venland. He is considered second in command of the Resistance.
Mark joined the Skylords at a young age. He later began serving the Eta Squad, serving under Commander Cid Fenix, soon joined by his brothers, Scott and Arnold. He and his brothers participated in the war against Venland, but Mark took charge of the Eta Squad when Cid resigned from his post, becoming the new commander of the squad.
After the war, Mark followed the advice of Cid Fenix and led the Eta Squad against the Skylords, becoming defectors, to his brother Arnold's chagrin. Langley eventually met Kitsuke Shokuji, who was searching for allies to his own cause and the two joined forces.