Flood (Earth-4001)

The Flood, designated as LF.Xx.3273 by the Forerunners (Latin Inferi redivivus meaning "the dead reincarnated") and referred to as the Parasite and the infection by the Covenant, is a species of highly virulent parasitic organisms that reproduce and grow by consuming sentient lifeforms of sufficient biomass and cognitive capability. The Flood was responsible for consuming most of the sentient lifeforms in the galaxy - including the vast majority of Forerunners - during the Forerunner-Flood war in ancient past, prompting the activation of the galaxy-sterilizing Halo Array in 97,445 B.C.

Originating as a corrupted form of the galaxy's most ancient custodians (the Precursors) the Flood reproduces and spreads by infecting other organisms, hijacking their bodies and nervous systems in order to transform them into one of many specialized forms. Through infecting sentient lifeforms, the Flood assimilates their memories and intelligence, and the species becomes collectively more intelligent as a result. Because of their frighteningly rapid growth rate, as long as enough hosts of sufficient biomass and intelligence are available, the Flood is effectively unstoppable.

All Flood forms share a single consciousness, which becomes progressively more intelligent and sophisticated with every sentient host that is assimilated. When enough hosts have been infected, the Flood consciousness becomes a Gravemind - a self-aware, highly intelligent entity that strategically commands all Flood forms in an outbreak. Due to this group consciousness, the Flood as a whole is more accurately described as a single, transsentient macro-organism rather than a collection of individuals directed by one or more controlling beings. In the absence of a Gravemind, the Flood possesses only basic coordination; they are incapable of forming complex strategies, and focus solely on attacking and infecting nearby sentient organisms. This stage of a Flood outbreak is known as the Feral Stage. At this stage, the Flood seek to create an assembly of biomass, calcium, and nervous system reserves, which leads to the creation of a Flood hive and the beginnings of a proto-Gravemind. The nature of the Flood's collective consciousness is similar to that of a hive mind, the Flood act as a unified entity, with no individuality that is inherent to other species; each vessel of the Flood works tirelessly to aid in the propagation of their species.

The Flood presents a highly variable and unconventional threat in combat, as it can infect and mutate dead or captured opponents into a myriad of deadly forms, effectively growing stronger as it weakens enemy forces. They are widely considered to be the greatest threat to the existence of life (or, more accurately, biodiversity) in the Milky Way galaxy.

History
The history of the Flood is the same as their mainstream counterparts up until the end of the Human-Covenant War in 2553.

Notable Victims

 * Private Wallace A. Jenkins
 * Private Riley
 * Captain Jacob Keyes
 * Private Manuel Mendoza
 * Lance Corporal Eugene Yate
 * Private Cranker
 * Gersten
 * Orlav
 * High Prophet of Mercy
 * High Prophet of Regret
 * High Prophet of Truth
 * Sub-Commander Bero 'Kusovai
 * Bok (Earth-4001)
 * Mendicant Bias
 * 2401 Penitent Tangent