"Have infection, will travel"
-Brother Death (RD: Gunmen of the Apocalypse)
Brother Death was the leader of the Apocalypse Boys.
When Kryten contracted the Armageddon Virus from a Simulant battle cruiser, he started to hallucinate himself in a wild west fantasy. He was the town's sheriff and was fighting a losing battle with a drinking problem. When Jimmy told him that the Apocalypse Boys were out in the street, he went outside to parley with them.
Their leader was a black-clad cowboy who did all the talking. His appearance was almost identical to that of the Simulant Captain who had deployed the virus, with the only differences being their clothing and eyebrows (the Simulants had two pairs). He spoke with a Texan accent and sported a bushy moustache.He introduced himself as Death and his brothers as Brother War, Brother Famine and Brother Pestilence. Death spat tobacco at Kryten's feet, causing a sizzling noise as it burned the decking outside the saloon. Kryten asked them what he could do to help them, at which point they drew their weapons and fired all around him. Death insisted that Sheriff Kryten leave town within the hour. He and his gang then rode out of town.
When Lister, Rimmer and The Cat mosied into town to help, they found themselves facing the Apocalypse Boys in a showdown in the street. Kryten recognised Death as a virus, which he confirmed by spreading the contagion to the AR console which the Dwarfers were using. He put his hand in the air in the sign of the horns and sent out a burst of multi-coloured lightning that extended the virus to the special skills being used by the crew.
Once Lister and The Cat had fled from the scenario, Death and his brothers advanced on Rimmer with their knives. They threatened to cut him into small pieces before Rimmer escaped as well. Kryten had to face the brothers alone and told them to go for their weapons. They all shot him multiple times, but he withstood it long enough to release the antidote which dissolved Death and his posse. (RD: Gunmen of the Apocalypse)
Behind the scenes
Death was played by Denis Lil, who also appeared in the same episode as the Simulant Captain. It is possible that the virus was created by the Captain in his own image or that Kryten's subconscious made his adversaries look alike.