The Undead Nightmare Collection combines the Undead Nightmare Pack, Liars and Cheats Pack & Legends and Killers Pack. 

• Undead Nightmare Pack: An entirely new single-player campaign following John Marston as he tries to find a cure for the highly-infectious undead plague.
• Liars and Cheats Pack: Multiplayer Poker, Liar's Dice, Horse Racing, Stronghold competitive mode and Explosive Rifle.
• Legends and Killers Pack: Nine new map areas, Multiplayer Characters from Red Dead Revolver and Tomahawk weapon.