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Information in this article may not be canonical to the storyline of the games or any other Sonic continuity.
Females closely resemble their plant ancestors, being mostly slender and having an arrangement of petals sprouting from their waists and buds—or bloomed flowers—atop their heads. Males are slightly larger than most of the inhabitants of Sonic's world, and are usually rather round, with short tails, small antler-like growths on their heads, and a colored ridge on the top of their heads; they are more similar to trees than flowers.
Characteristics and culture
Members of this species evolve into trees at some point in their lifetimes, perhaps a first stage of death or old age.
Powers and abilities
Male members of Cosmo's species have the ability to transform into colossal tyrannosaurus-like creatures which is referred to as the "final phase" or the "Mover Mode." In this form, they gain immensely enhanced strength and durability, but maintaining this transformation would drain them of the own energy and using it for too long would prove fatal. However, Earthia invented a crystal which prevents them from going to final phase.
For untold years, Cosmo's species was locked in a galaxy-scaled war against an unknown foe. Over the course of the war, the tides began to turn against Cosmo's species as countless of their kind died, either by the hands of the enemy or from entering the final phase to combat the enemy. Understanding that they would perish one way or another if they stayed on their home, the planet's leader Earthia decreed that they would have to leave Green Gate to survive and find a new home. Earthia's husband and renegade scientist Lucas however, was unwilling to abandon the fight and risk further universal destruction. In the end, dissension was created, with all the known males gathering on Lucas' side and joining under his command in the refusal to leave the planet, while Earthia commissioned the creation of a spaceship that could take a mass number of the females into space.
In an effort to combat the enemy, Lucas stole their world's Planet Egg. Willing themselves to undergo unnatural evolution, Lucas used the Planet Egg's power to stabilize his and his followers' evolution process into the final phase, allowing them to use their monster forms without limit. Stealing the Planet Egg caused Green Gate to slowly withered away, which Earthia soon noticed. Devastated at what Lucas and the others had become, Eathia and the females abandoned their world and their mutated comrades to destruction by their enemies.
As Lucas and hundred of other males continued to fight the enemy on Green Gate, Earthia had their world bombed with nuclear weapons to stop Lucas and the others before they could endanger the universe. However, five males, including Lucas, survived the onslaught. These five were to become Dark Oak and his henchmen through a finishing phase of their evolution and became the leaders of the Metarex. Earthia and the females eventually escaped into space, creating a colony upon which Earthia's last daughter Cosmo was born. Determined to rid the universe of all non-plant life and to have revenge on their former colleagues, the Metarex hunted down and attacked the ship carrying the surviving females, all but exterminating them.
The ship was destroyed, leaving only six known specimens of the race alive: Lucas, reborn as Metarex leader Dark Oak; his commanders Red Pine, Yellow Zelkova, Black Narcissus and Pale Bayleaf; and Earthia's daughter Cosmo. After the final battle against the Metarex, Lucas and all his followers were killed while Cosmo sacrificed her life to ensure this victory, leaving their species virtually extinct.
- Members of Cosmo's species are widely known on the Internet and by fans as Seedrians. The origin of this term is unknown, though presumably inspired by their plant-like nature. However, the name is currently unofficial.
- Females of Cosmo's species resemble the creatures from "Maginaryworld", a dreamworld in Sonic Shuffle. For example, Void highly resembles Cosmo.
- Because they are plant-like creatures, it is possible that the members of Cosmo's species can be reborn. In the English dub, Cosmo lets Tails know of this fact before he had to sacrifice her.
- As a species of anthropomorphic plants, Cosmo's species could be seen as an opposite or a counterpart to Sonic's species, who are anthropomorphic animals.