#aeion

Though severely wounded organisms will leak aeon into the air, a lot of the stuff remains permanently locked into the tissue of the life-form even after death. Sometimes these bodies will pile up without being eaten or completely decomposed and will eventually be buried and carried deep down into the planet’s crust by geological processes. Over millions of years, these undedground deposits of dead biomatter will be compressed and warmed to ridiculous amounts and pressure and heat, in the exact same kind of process that creates coal or oil on earth. For aeon-based biomatter, this process breaks down the extraneous materials and chemically transforms the aeon energy itself into a slightly different form, which forms solid chrystaline structures. Hundreds of massive aeon crystal deposits exist under the surface of SR388, still buried in the rock. Now if that crystal should be released from the pressure of the rock around it and allowed to react with the atmosphere of SR3-88… well, that’s how you get an X parasite. The solid yellow glow you can see coming from the cavern ceiling in chozo memory 04 is actually coming from the giant crystal deposit unearthed by the chozo’s diggerbots and diggernaut, the crystal that birthed the ancestors of all of the X parasites alive in the universe at the time of Fusion. This is why the most basic X parasites share the same distinctive yellow glow as pure aeon. They practically ARE pure aeon (90% fossilized aeon, 10% other partially fossilized biochemicals. They are highly concentrated with aeon).

Merroids are designed to kill X parasites by reversing the chemical process that turned them into X parasites in the first place. When an X parasite attempts to posess a metroid (or when a metroid forcibly absorbs an X parasite) the metroid will first separate the aeon, and then perform a chemical reaction that reverts the fossil aeon to “fresh” aeon, the same form it takes in normal SR388 lifeforms, making it unusable to the X. The metroid uses some of the aeon energy to keep itself ticking, but most is stored internally, theoretically for the chozo to harvest later. Finally, the metroid metabolizes the little bit of leftover goop from that 10% other stuff, which provides most of the metroid’s nutrition. The ability of metroids to sap body fluids and aeon from non-X organisms was a survival tool implemented to help them through long periods of hunting without finding any X.