The Sacrifice takes place after Blood Harvest, and is considered to be the prologue to The Passing, as both campaigns are connected to each other. The DLC is free for PC players, while for Xbox 360 players, it comes in two separate packages on Xbox Live (one for Left 4 Dead and one for Left 4 Dead 2), and costs 560 Microsoft Points for each one.
The campaign's name comes with the obvious interpretation that one of the Survivors has to sacrifice themselves in order to enable the survival of the team. Canonically, Bill is the one who makes this choice, as seen by his unfortunate appearance in The Passing's finale inside a generator room, as well as the comic. The tagline, "It's your funeral," refers to the idiom "it's your funeral", basically meaning someone may have made a bad choice, and if they follow up on it, they will have to endure the direct consequences regarding that choice. Should the survivors decide to sacrifice nobody, a continual horde and endless amount of tanks will spawn until they eventually overrun the survivors.
Unlike other campaigns, The Sacrifice's Achievements can be obtained separately on both Left 4 Dead and Left 4 Dead 2. Two of the Achievements, SUPREME SACRIFICE and KILL BILL, are only obtained by the player who sacrifices themselves in Left 4 Dead, while in Left 4 Dead 2, it counts for the whole team.
The Hunting Rifle in Left 4 Dead (commonly referred to as the Sniper Rifle prior to Left 4 Dead 2, which the interview may have made a mistake on) has been rebalanced to match its counterpart in Left 4 Dead 2.
SUPREME SACRIFICE does not feature a rescue vehicle unlike the other campaign achievements (not counting Last Stand). This is because the campaign is completed without a rescue vehicle.
The finale introduces a new way of completing a campaign. First, the the Survivors must start up three generators; second, they must get on the bridge and raise it; and finally one team member must sacrifice themselves restarting a generator in the face of impossible odds.
The finale of this campaign takes place in the same area as The Port from The Passing. As a result, the Survival mode level is incredibly similar.
This campaign has an unusual scripted amount of Tanks. The first is a Tank in a train car on The Docks, the next three come from the three generators in Port Finale which the Survivors will face in succession while waiting for the bridge to open up, and the final four scripted Tanks appear after the Survivors have got onto the bridge and raised it halfway.
This is the only DLC to be released for both Left 4 Dead and Left 4 Dead 2.
As is the case on the Dead Air poster, The Sacrifice poster also illustrates Bill without his signature cigarette.
Notably, the sunlight from behind Bill forms a halo around his head. Whether this is coincidence or intentional (as it seems to symbolize his canon death) is not known. Seeing as the Achievement "Kill Bill" also does this, it would seem intentional.
So far, this is the only campaign poster to feature Francis with his gloves on.
It is also the only campaign poster to have Zoey carrying a weapon other than her pistols.
Unlike in game, Zoey's hair seems to not be in a ponytail in the poster, and is instead loose and wavy.
In the campaign poster, Francis is seen holding a combat shotgun and Bill seem to be holding an AK-47, both weapons from Left 4 Dead 2.
Francis is also holding the combat shotgun left-handed instead of right-handed, which may suggest that Francis is ambidextrous like Louis.
In the intro trailer, a safe room door can be seen off its hinges, suggesting that there was nowhere to run to.
In all three Chapters, the Survivors make oblique references to events that took place in the comic (Zoey berating Bill for leaving the doctor to die, for example), but they never specifically say what happened or who was involved.
The Sacrifice is the second DLC to release additional community lines recorded by Valve for Custom Campaigns. This time, only Bill's voice actor recorded community lines (in addition to all his other new lines for The Sacrifice, along with Left 4 Dead 2Special Infected cries) to fit in with the other Left 4 Dead community lines referencing the cold.
Bill's voice actor also recorded twenty movie lines which appear to be unused, and either left in by accident or for the community to use. All of them appear to be themed on his dying words after he is mortally wounded by the multiple Tanks and waiting for them to approach him.
There is a mistake with the license plates on the cars for the Left 4 Dead version of the campaign. The setting is in Georgia, but the plates read Pennsylvania. This might be caused by an oversight by one of the developers that reused the cars in Left 4 Dead 2 in that version of the DLC and might have forgot to add the Georgia cars in the Left 4 Dead version of the DLC which then reused the cars from Left 4 Dead, which have Pennsylvania plates.
Although it could be intentional as it could be cars from Pennsylvania fleeing towards Georgia.
Unusually, despite taking place around the same locations as The Passing, there are no Golf Clubs anywhere.
This is the only campaign in Left 4 Dead to take place in the evening (as opposed to night, midnight, or early morning as the past campaigns have been). This modifies gameplay (e.g.) the Infected can be first seen at longer ranges than previously, although the Witches are stationary rather than wandering around.
The game designers make clever use of a "river fog" effect that changes in density to signal the passage of time.
In the Left 4 Dead 2 version of The Sacrifice (along with the Left 4 Dead 2 version of No Mercy), the Survivor Bots' preferences for Tier 2 weaponry have changed: Zoey prefers Assault Rifle variants, Francis prefers Hunting Rifle variants, Louis prefers Auto Shotgun variants, while Bill remains unchanged, still preferring Assault Rifle variants. This is most likely because the Left 4 Dead Survivors take the gun preference of their corresponding Left 4 Dead 2 Survivor (Bill to Nick; Louis to Coach; Francis to Ellis; Zoey to Rochelle).