Valve announced the new add-on for its co-operative zombie thrillers — "The Sacrifice," in development for both Left 4 Dead (L4D) and Left 4 Dead 2 (L4D2) — is due for release on October 5, 2010.

"The Sacrifice" is the prequel to "The Passing," and takes place from the L4D Survivors' perspective as they make their way South. In addition to advancing the story, "The Sacrifice" introduces a new style finale featuring "Sacrificial Gameplay" where players get to decide who will give their life so the others may live.

The Sacrifice DLC for L4D1 is a seperate download than The Sacrifice for L4D2.

In The Sacrifice for Left 4 Dead 1 gamers receive the complete Sacrifice campaign with maps playable in Campaign, Versus, and Survival.

In The Sacrifice for Left 4 Dead 2 owners receive "The Sacrifice" campaign playable with the Left 4 Dead  Survivors. In addition, those with Left 4 Dead 2 receive L4D's "No Mercy" campaign. Both campaigns are playable in Campaign, Versus, Survival, and Scavenge modes and both will feature the Left 4 Dead 2 Special Infected, items, and weapons. Yes, Zoey with a chainsaw!

Targeted for release on October 5th, "The Sacrifice" will be available for download on Xbox Live for 560 Microsoft Points and free to all PC gamers.

For more information, please visit www.l4d.com.