Hydra

"They were like snot globs, or hair gel.... or.... or jello! Yeah, we fought evil, mind-controlling jello!.... I don't think that HIGHCOM is going to believe us"

- An anonymous marine in the Last Battle of Ceres

The Hydra are a parasitic species of unknown origin. They are similar, though more dangerous than, the Flood.

The Precursor-Hydra War
At some point in ancient history, before the firing of the first Halos, the Forerunners ran into the Hydra. Whether they were discovered before or after the Flood is unknown, though it is believed to be after, as the Sentinels that deal with the Hydra seem to be of a slightly newer design. The Forerunners, now pressured by the double threat of both the Flood and the Hydra, attempted to quickly quarantine the Hydra while they were a still small force. They succeeded, placing them in containment and research facilities on several isolated planets and facilities. In the short time that the Forerunners had left before they decided to fire the Halos, they studied the Hydra and tried to find a weakness. While they couldn't find anything that would kill the Hydra, they did find out that they had a weakness to the cold. Shortly before the first firing of the Halos, there was one outbreak in the containment facility now known as the Satellite. During the outbreak, many of the Forerunners were killed and the Monitor of the Installation, 13198 Ensnared Cadaver, was captured and taken over by the Hydra. The Forerunners quickly set the entire station into a deep freeze. No contact with the Hydra would be made until July 25th, 2554 during the Battle of the Satellite.

Physical Description
The Hydra appears to be made of a semi-solid substance that is semi-transparent. It will go inward if pushed on, making melees nearly useless unless it goes all the way through. They have virtually no organs, save a central nucleus that moves through the rest of the body. They can reproduce by splitting one body into multiple bodies or by absorbing other things. They can either infect another being to create a Flood-like zombie, or they can rearrange their own bodies to create various combat like forms, such as worm forms, total melee forms and various others.

Biology
The Hydra, a parasitic species, has the ability to infect organisms or take over machines, effectively controlling them. Infected organisms will usually go through a variety of "forms", usually even changing between several different ones. A Hydra's chosen form depends on the species of creature infested, and the usefulness of the infected body.

The Hydra have two different pathways of reproduction and survival: One is through the infection of other species, and the other is for a Commander form to spawn Cell forms. Both choices require extra biomass though.

Organic Infection
A Cell form will search out and find an organism of any sort, and then attach itself to either the head or the chest area. If the Cell form attaches to the head, it will seep through either the pours, eyes, ears, mouth or nose and surround the brain. From there, it injects its' DNA into the brain cells to the point when it is able to merge with the brain cells, with the nucleus taking the place of the brain, and thus gaining control over the rest of the body. If the Cell form attaches to the chest, it will seep in through the pours and take control of the lungs and heart, effectively stopping all breathing and blood flow, killing the host. It then will take the rest of the body over by inserting its' DNA into the rest of the cells. Once the body is entirely controlled by the Cell form, it grows organs that will produce more of its' gel-like biomass and then excrete it out the pours, covering the entire body and thus making it slightly resilient to gunfire, as it is able to stop the projectiles before they penetrate the vital organs. The slime cannot stop sharp objects though, which are very useful against infected Hydra forms. Usually, the Cell form will add extendable tentacles near the wrists. While the tentacles usually stay a few inches long, they have been known to extend to 15 feet at most. In addition to these traits, the Cell form enhances all former characteristics of the host, such as speed, strength and jumping capabilities.

Mechanical Takeover
This form of infection is not necessary, and requires instruction directly from a Commander form.

Other forms
Infection is not the only option for the Hydra. They can merge, divide and rearrangement their mass to create different forms.

Cell form


The most basic Hydra form, the Cell form is used to construct every other form of Hydra. It can merge to form larger forms and divide to create another Cell form.

Spawner form


The Spawner form births Cell forms. It is immobile, staying in one place all the time and is fed raw material to allow it to build up enough new mass to separate it off as a Cell form. Spawner forms can be created by two means: several Cell forms merging, or the infection of a host inadequate for combat, such as a Grunt.

Infected Lifeforms
Note that not all lifeforms can be infected and enter combat. Some are used as food/material for other forms, while some become other forms, such as the Spawner form.

Infected Bujkowe
The Bujkowe were the most commonly seen Hydra-infected lifeforms, as they were the first encountered by the Hydra.

Commander form
The Commander form is the ultimate Hydra form. It is the puppet master, and has been shown to be able to control all Hydra within an entire system.

What If?
In the Alternate Universe of Halo: What If?, the Precursor-Hydra War went on as usual. But, once the Forerunners were killed by their Sentinels, the Hydra were left without opposition. So they spread across the galaxy, and soon found the Flood, who were also left unopposed. All Hydra forces, and all but one hive of Flood forces engaged in an enormous battle in the Ceres system, and the Bujkowe suffered from it. Soon, they managed to activate the Ceres installation, but they escaped on Forerunner ship before the blast destroyed them. The blast from the installation's weapon destroyed all Hydra forces. None were left.

Behind the Scenes

 * They were named the Hydra after the mythological beast which grew back two heads for every one that was cut off.