The Chozo are a fictional species found in the Metroid series. Despite the species hardly appearing in gameplay segments of the series, the Chozo remain one of the prominent elements of the franchise and are important figures of the Metroid lore. The Chozo are a bird like, immensely intelligent and peaceful race who rescued the series' protagonist Samus Aran after her colony was destroyed by the Space Pirates. They crafted her power suit which would give her the chance to visit planets that had an environment unsuitable for her, as well as give her abilities unknown to any organization, quickly leading her to become one of the most feared beings in the universe to those who do bad. During the course of the game, they leave traces of their history behind, though there location has remained a mystery for very long, with some speculating that the entire species was wiped out.
For years the Chozo flew to the farthest reaches of space, offering their technology and vast amounts of scientific information to races such as the Luminoth, the Reptilicus, and various others. Their race would construct cities so beautiful that none could compare. Their contributions to the scientific front were appreciated among the many races. On the various planets that they would take rest, the Chozo would construct beautiful statues crafted by the most experienced of the species. The purpose of the statues varied. Some are crated as a relic, to remind those that view it that there was once peace on a planet so engulfed in violence and war. Others wielded an unknown strength that could hardly be understood by those who didn't create it. And others could prove to cause havoc upon those who would spoil the statues, yet deliver great fortune upon those who respected it.
Upon landing on Elysia they built the robotic race known as Elysians, which would serve them on their quest for cosmic knowledge. Upon departing they would travel to a planet known as Tallon IV, where they would seclude themselves from the rest of the world, taking notice of the disturbing trend of moving towards technological advancements and leaving behind their old, spiritual ways. On Tallon IV things would change, and their spirituality, which had over the years decreased, would return. The temples on Tallon IV would be built of raw materials found on the planet. They explained that while they knew much of technology, in their new chapter they would leave it behind, managing to exist as the creatures of Tallon IV do. Despite their capacity for building structures of a grand scale, they would create buildings made of stone, bridges of trees, and would gather materials needed from nature as they primitively did years ago. They would become, as they explained, "just one more group of creatures in the knit of nature". The purpose of this peculiar choice was the hope of increasing their vast knowledge of the universe.
In their civilization lied a wellspring that brought fourth the purest water of Tallon IV. As the Chozo's knowledge of life was enhanced through the course of time, they began to have glimpses of the future and of the past. In these visions, the treasure fountain spew fourth darkness in lieu of water. The Chozo knew not what this prophesy foretold, though they sensed that it did not bode well for their future. For now, however, they would leave the planet. Regarding it as the most sacred of their many homes, they would depart from Tallon IV, remembering of their time on the planet, and their long seclusion from other races and from machines. They would keep watch on their planet, however, and would return if there ever happened to be a force that would prove harmful to it.
Light years away, a planet in an unknown galaxy, was being created. Considered an entity itself, the planet became known as Phaaze. From it came the substance that would be known as Phazon. A meteor from the dastardly planet was launched, and would eventually find its way to Tallon IV. Crashing on the surface, the meteor would launch the element across the planet, and those who were exposed to it would either die or experience mutations. The Chozo returned to the planet and used all of their power to try and alleviate the effect of Phazon, though all they could do was create a temple which would cover the site of impact. Grasping onto the hope that someday a warrior would come to Tallon IV to destroy the Phazon completely, they scattered various objects that they had built across the land. They left the planet, disclosing their location to no one.
They assisted those who did good, and would in one point in time act on a distress call sent out from a K-2L colony. By the time they arrived, everyone had been killed, excluding a small child by the name of Samus Aran. They took her in as their own and raised her, giving her a power suit with which she would do good. As an adult Samus Aran would eventually leave, becoming a bounty hunter who was typically employed by the peace keeping Galactic Federation.
Chozo Ghosts were enemies found in Metroid Prime. In the game, the player would have to defeat them using a wide range of weapons. Due to them traveling through different dimensions, Samus would have to use x-rays to find them. Their violent behavior is said to be because of the Phazon in the environment. Early in the game the Chozo would appear exclusively in the Hall of Elders, though after acquiring the Ice Beam, they'd appear throughout the Chozo Ruins, frequently appearing in pairs of two or groups of three. The player could defeat them by using the Power Beam, the Ice Beam, or the Plasma Beam.
"Spectral entity. Bioelectric field invulnerable to natural energies. As these entities phase in and out of existence, the only way to track them accurately is with x-ray scanning. This partially phased nature makes them invulnerable to natural energy types, such as fire, ice, and electricity. Their aggressive and erratic behavior is most likely due to the corrupting effects of Phazon in the Tallon IV environment. They appear to be drawn to Chozo religious sites, where they wreak havoc upon anything that dares enter the area."
- Chozo Lore - The complete Chozo Lore as seen in Metroid Prime.