"The Flood is composed of a variety of specialized forms, each filling a different role in combat. The most basic Flood forms are the infection forms, which come in various types and infect hosts by hijacking their bodies and nervous systems. Infected hosts then undergo a rapid series of transformations, becoming lethal combat forms. Combat forms are used to subdue and secure additional hosts for infection, and once they have outlived their usefulness as warriors, they transform into carrier forms, spreading the Flood by spreading more infection forms."

( This collection contains all the best flood mods for L4D2. simply subscribe to all and make sure they are enabled in the addons menu in game. )