Flood spore

"One single Flood spore can destroy a species."

- Rtas 'Vadum

Flood spores are the most basic of Flood forms that are crucial in the formation of Flood hives. Spores are also used as methods of suffocating future hosts and clearing the area of uninfected hostiles. Flood infection forms also utilize encapsulated Flood cells referred to as spores when infecting other life forms.

Description
The spores that have been witnessed the most frequently are a variety that will stay airborne, and will perform functions such as clogging air filtration systems, allowing for more efficient access to host organisms. If a spore lands in an area that can support it, it will form Flood growth pods. If the area does not have enough biomass to support a growth pod, the spore will spread over floors and walls until it covers as much as it can. When infesting a location, the Flood often uses spore mountains or spore capsules to quickly disperse spores into a planet's atmosphere and thus expedite the conversion of the local biota.

While the infection forms are often employed by the Flood as its standard means of infection, it is possible for a compatible host organism to be infected by Flood spores alone, especially if it is an active state rather than the normal passive one. The spores will enter the body and go about interfacing with the host's biology, consuming the victim's biomass and replacing it with Flood biomass, leading to biological transformation. The Special Operations Elite Kusovai was infected when he inhaled Flood spores. Due to the fact that he had been infected in this secondary manner, his rate of mutation was far slower than that done by an infection form, and he was not physiologically distorted in the same manner as those originating from the primary means of Flood infection are. These consequences of infection via Flood spores is next witnessed when the Prophet of Truth was infected by the Flood at the close of the Battle of the Citadel.

Trivia

 * Flood spores can be seen in Halo 2 and Halo 3 on levels where there is extensive Flood infection, such as the Quarantine Zone and Cortana.
 * In Halo Wars, there is a configuration of the Flood spores that are referred to as "spore clouds", and they only appear after a Flood growth pod has been destroyed, or a Flood launcher fires flood biomass at opposing forces. Infantry that have been attacked by these spore clouds will be transformed into Flood combat forms, which renders the Flood launchers a formidable threat to attacking infantry. Whether or not this is an actual function of the spores or if it is simply an artifact of gameplay, such as the non-canonical presence of shields in Red Team's MJOLNIR armor, is unknown.
 * In Halo 4's Flood mode, the infected Spartan IVs appear to be infected via spores, as they lack the infection form's tendrils, and the method of infection is direct contact with a combat form.

List of appearances

 * Halo 2
 * Halo Graphic Novel
 * The Last Voyage of the Infinite Succor
 * Halo 3
 * Halo Wars
 * Halo: Combat Evolved Anniversary
 * Terminals