This game is rated ESRB: Mature 17+ for Blood and Gore, Intense Violence and Language.
Released in 2010 for PC and Xbox 360, The Sacrifice is a downloadable content pack for Left 4 Dead 2 that ports two campaigns from the original Left 4 Dead: The Sacrifice and No Mercy. The addition was motivated by narrative context — The Sacrifice depicts events that lead directly into Left 4 Dead 2's campaign The Passing, and Valve wanted players to access that backstory without requiring ownership of the first game. No Mercy was included due to its status as the most popular campaign in the original title. Both campaigns support all available game modes and cast players as the original Left 4 Dead survivors, while incorporating the expanded roster of items and Special Infected introduced in Left 4 Dead 2. The pack also adds five achievements, mirroring the count included in the simultaneous Left 4 Dead release of the same content.