From their website:
Survivors is a 28 card Character Replacement Upgrade for Chaos Isle: Zombi Deck. The deck contains every Character ever made for Chaos Isle, including those from the Promo Set, 6 brand new Characters, and the all-devouring Brood Mother, a killer of Zombies and Characters alike with her own special set of rules. All cards have brand new artwork and design. Also included are rules for Outbreak: an entirely new way to play the game using strategic cooperative play, and Split Personality: a new way to enhance Mission-Based game styles. Requires the original Chaos Isle: Zombi Deck core game to play.