Lord Arthur, played by Marcus Gilbert, is a character in the film Army of Darkness.
Lord Arthur is at war with Duke Henry the Red. When Ash Williams arrives via portal to the middle ages, he is captured by Arthur's men, mistaking him for one of Duke Henry's men. Upon Ash's arrival to Arthur's castle, he is thrown in a pit where he kills a Deadite and regains his weapons from Arthur's Wise Man. After demanding that Henry and his men be set free and killing a Deadite publicly, Ash is celebrated as a hero.
When the Army of Darkness comprised of deadites arises, Arthur joins forces with Duke Henry and Ash and defeat them. The victory brings peace between Arthur and Henry.