Eyons produce a focused energy beam which moves and will do minor damage if Samus comes into contact with it. Why it produces this beam, other than to hinder movement, is a mystery. If any form of weaponry is fired near or at the Eyon, a membrane will close over its "eye" and disrupt the energy beam. A charged shot can destroy it completely.
It is possible that the Eyons are not biological organisms at all, but cybernetic security systems designed by the Chozo. However, the Chozo are said to have traveled to Tallon IV to eschew technology and return to a simpler way of life, suggesting that the Eyons are bio-engineered, much like the Cyrlic trees found on Tallon IV. The Eyon's organic appearance supports this theory.
In appearance, Eyons resembles gigantic eyeballs. They are largely tan-colored, have little to no coloring in their iris, and have a vertical pupil like that of a reptile or a cat. They seem to have some sort of root system that attaches them to surfaces. Various carvings very similar in appearance to Eyons appear on some walls of the Ruins. It is unknown if these are "inactive" Eyons or simply creations made in their likeness.
Immobile organisms entirely composed of ocular tissue.
Immobile organisms entirely composed of ocular tissue. Capable of launching sustained energy beams when active, the Eyon is sensitive to light and will close shut if a bright flash ignites nearby.
- The name "Eyon" may be a portmanteau of the words "eye" and "ion."
- The texture of the Eyon's eye is reused in Metroid Prime 2: Echoes as the eye of a creature known as a Webling.
- The Corrupted Sentreyes were built by the Luminoth, who are known to have met the Chozo from Tallon IV at some point in the past. This leads to theories that both sentient races exchanged cultural information, thus possibly allowing the Luminoth to create a mechanoid based on the Eyon.
- Jack Mathews revealed in a 2015 livestream that the Eyons originally had no gameplay purpose, and were created by one of Retro Studios' artists purely for decoration. Their laser projection abilities were added in later, to give them a more interesting role.
- The Watery Hall is the only place where deactivated Eyons can be seen; they appear to be dormant until Samus obtains the Charge Beam, at which point they spring to life.
- In the North Atrium, there appears to be a fossilized Eyon.