The Flood, otherwise known as Inferi redivivus by the Forerunners and the Parasite by the Covenant, is a species of virulent, savage, parasitic organisms that thrive by consuming sentient lifeforms of sufficient biomass and cognitive capability.

The Flood are believed to be of extragalactic origin by the Forerunner, and their origins and purpose of coming to the Milky Way galaxy are unknown, but are presumably to infect all sentient life in the galaxy.

In regards to every outbreak of the Flood, there exists numerous stages the parasitic organism undergoes which are feral, coordinated and interstellar with the possibility of another ...