Imagine a situation where two vicious and dangerous species come into conflict. Two species driven by the need to consume, and driven by a collective conscious. Two species who’s presence on a planet usually means the annihilation of life on that planet. We are talking about the species known as “The Flood” from the Halo universe, and the ravenous Tyranids of the Warhammer 40k universe. If these two species were to encounter each other which of the two would come out on top?

First let’s take a look at the two species we are dealing with.


Infection forms attack Master Chief Source:

The Flood are a parasitic organism from the Halo universe with the sole purpose of consuming/infecting sentient organisms of sufficient biomass, and cognitive capability. The Flood is not like anything seen in the Milky Way as it is actually an extragalactic organism. The Flood is extremely virulent, and once a Flood infestation has made itself known, it is near impossible to prevent its spread throughout the world which it has infected. Although the Flood can infect most organic organism with complex enough central nervous systems, they tend to prefer assimilating sapient organisms. Their preference for infecting intelligent organisms comes from the fact that the intelligence of the hivemind comes from the assimilation of biomass, but the intelligence seems to be correlated with the intelligence of the organisms assimilated into the collective consciousness of The Flood.

As The Flood grows so does its intelligence, with how intelligent the flood is depending on the amount of sapient beings it has taken into its collective. What makes an intelligent flood so dangerous is that the entire species acts as one organism with the actions of each individual controlled by a hivemind.  Like any other super organism (such as ants) The Flood is composed of several specialized individual sub-types.

  • Feral Forms
    • Infection Forms – Most commonly seen, responsible for spread of the disease.
    • Carrier Forms – As suggested by the name, these forms are used primarily to transport Infection forms in order to spread infection of the disease.
    • Combat Forms – Sentient being that has been infected and mutated by the Flood. When Feral they can be easily defeated, but become incredibly dangerous and coordinated when under control of a Gravemind.
  • Pure Forms- These forms are not the result of infection, but rather on composed entirely of Flood biomass. These forms have a calcium based exoskeleton that makes them more resilient to damage.
    • Stalker Forms
    • Ranged Forms
    • Tank Forms
  • Advanced – These are different levels of Flood hivemind with intelligence levels being determined by the amount of sapient organisms taken into its collective biomass.
    • Proto-Gravemind
    • Gravemind
    • Keymind
  • Misc

On the other side of this encounter we have the Tyranids. Like The Flood, the Tyranids are an extragalactic species and before its arrival in the Milky Way have already wiped galaxies clear of all life. The main motivation for a Tyranid invasion is the consumption of all organic organisms. Where The Flood requires the infection of sapient life to grow in intelligence, the Tyranids show no preference, but rather devour ALL organisms. Tyranid organism are bio-mechanical in that some organisms incorporate firearms and edged weapons as part of their biology, even their space ships are simply a another form of Tyranid organism. Unlike the Flood, the Tyranids are capable of space flight on their own, without the need to infect and assimilate organisms in order to acquire the tech. Once Tyranids have consumed an entire planet’s organics, their conquest is taken back to the hivefleet where it is incorporated into the creating of new Tyranids forms.


A Genestealer Cult begins its revolt Source:

Unlike Flood invasions which require the infection of hosts, Tyranid invasions follow a precise pattern always initiating the process with reconnaissance. This stage is usually undertaken by a Tyranid form known as a Lictor which is bred to specialize in recon and stealth. Another approach to recon is the use of Genestealers. The Genestealer form usually inhabits space hulks where they wait for the arrival of unsuspecting individuals. When encountered, Genestealers will implant their victims with their genetic materials leading their hosts to become the unknowing, and unwilling accomplices to the Tyranid’s conspiracies. As hosts reproduce they pass the Genestealer genes through to their offspring, which do then go on to pass the genes further down the genetic line. As each generation comes to pass the effects of the Tyranid genetic material makes itself known more and more. Mutations arise throughout the generation, until eventually pure strain genestealers result. The infected, and his descendants are also driven by a strong desire to worship the Tyranids in what is known as Genestealer Cult. The Genestealer Cult spreads throughout all levels of Imperial Society, infiltrating governments, and other houses of influence.Eventually once the cult has grown enough it acts as a beacon to nearby hivefleets, which begin their journey to the infected planet. The cult acts to weaken planetary defenses, and ultimately allow the Tyranid invasion to begin its consumption of the planet.

Tyranid sub-species are too diverse to name, but they came in various shapes and sizes, each with their own role to play. For instance, there are the small maggot-like rippers which engorge themselves before throwing themselves into digestive pools to deliver their collected organics into capillary towers. Then there are the large Bio-Titans taller than buildings and capable of taking on Squads of Space Marines on its own. Each individual species is highly specialized for its specific roles within the superorganism, however, Tyranid forms are only effective when they remain in contact with the hivemind. When Tyranid forces spread across the surface of a planet during an invasion, they maintain a connection to the hivemind through the use of synaptic creatures which extend the range of the hivemind. Without a connection to the hivemind, Tyranids will become feral, and rely on base animal instincts to survive. In fact, only a few Tyranid creatures are capable of operating outside of the reach of the Tyranid hivemind, name the Genestealers to mention earlier.

So, in an encounter between these two species in which one would win the resulting battle? That depends on the circumstance under which these two organisms meet.


Tyranid invasion Source –

In a scenario where the Tyranids come across a Halo installation and encounter the flood before it has the chance to infect any sapient organisms then the fight will go to the Tyranids. The Tyranids would board the Halo, at which point swarms of rippers would be unleashed. These small maggot like organisms would immediately begin eating any and all organic life; grass, trees, fish, birds, and so on. No life would be safe. As the Tyranid forces spread across the installation they would come across the Flood in their infection form. a form in which they do not have the thought capacity to implement advanced tactics, or coordinate any sort of counter-attack. Even if they managed to invade one or two Tyranid forms such as a Hive Tyrant, the endless swarm of uninfected Tyranids would be enough to deal with any infestation. The moment one Tyranid became infected it would simply be seen as more food for the hivefleet to devour and incorporate into its feast. The only way that the Flood would have a chance would be to cut off a significant chunk of Tyranid forces from the influence of the Hivemind and infect them. Given that infection forms would not have the tactical know how it is unlikely that The Flood would be able to cut off enough Tyranids to develop a strong enough fighting force. In this scenario, the Tyranids also have the advantage of not needing to infect sapient organisms in order to become an efficient fighting force, while The Flood does. The Flood would never have a chance.

In a Scenario where the Flood have developed a Keymind, the flood would have a greater chance, but I feel that ultimately it would still go to the Tyranids. The situation here would be one where the Flood has taken in enough sentient biomass to develop the intellectual ability to react tactically to a Tyranid invasion. For the sake of argument, we are going to assume that The Flood has taken over a human colony from the Halo Universe, and have access to weapons, planetary defense systems, and a few ships, along with having reached a Keymind level intelligence. Under these circumstances, with such an advanced intelligence it becomes more plausible that the Flood could potentially be able to separate a Tyranid force away from a synapse creature, thus severing its contact with the Hivemind, during this brief separation it would be possible for infection forms to infect the isolated Tyranids in order to incorporate them into their ranks, and thus give the Keymind some inclination as to the nature of the foe that it is facing. Or given the advanced intelligence of the Keymind, it would be possible for the Flood to identify that the best way to bring down a Tyranid invasion is to destroy the swarm’s link to the Hivemind through the destruction of synapse creatures, leading them to more targeted attacks. In this scenario, the only chance that the Tyranids would have is if they managed to overwhelm the defending Flood forces through sheer numbers. The only chance for a total victory the Flood would have is if they managed to take whatever ships they did have, and used them in such a way that they managed to destroy the Norn-Queen in her vessel. This would leave the Tyranids without leadership which would make any remaining Tyranid forces revert to a primitive animalistic state. The remaining forces would then be easy prey to any remaining Flood forces.

If the Norn-Queen is not destroyed though, the Flood forces on the ground would not be able to defeat the Tyranids for the simply fact that Tyranids can use all organic biomass to create more Tyranids. So as Flood forces fall in battle, unless they have a way to replenish their numbers, such as by being able to infect new sapient hosts, then it becomes clear that the Flood will simply lose through attrition. The Tyranids, on the other hand, would be able to continuously replenish their numbers as they devoured anything from grass to trees, to dead combatants on both sides of the war.

This is my take on what would happen if Tyranids and The Flood ever came into contact, obviously, I may be a bit biased towards the Nids as it is no secret that I love the Warhammer 40k Universe. However given that they are not limited in their reproduction by a need to devour a specific type of life form, I feel that they are the more dangerous foe. Tyranids also have the advantage of not needing to build up their hivemind until it reaches an acceptable level of intelligence before it becomes a threat, they are ready to go from the get-go. Finally, given the vast number of Tyranid bio-forms, and how specialized each form is to their job, I feel that the Tyranids are just more prepared, and thus would clearly win in a war between the two.