Seasonal Experimentation
When the Spirit Beasts arrived to the Eden Spheres, the Seasonal Sisters each believed their request had been answered, especially once they realized they could have more direct control over the Spirit Beasts and could shape them to suit their realms and use them as avatars instead of the more abstract elemental bodies they used their authority of their Spheres to construct.
Of them, it was naturally the creative and artistic Spring who was the most interested in shaping the pearlescent slimes into creatures of her own. Her presence filled them and usurped the power of the creatures, their forms expanding and shifting according to intelligent design rather than the pressures and hazards of their environment. Spring seemed to have a favor for small and cute animals for her lively and vibrant domain, small white rabbits with a small metallic black horn soon hopping around the fields while chipmunks and squirrels scurried around the trunks and branches of trees, chasing each other as they looked for food. Yet there was also majestic deer whose bucks were gifted with impressive antlers that were both impressive in an aesthetic way and practical way. Butterfly and bee like creatures flew through the air, going to flower to flower and assisting in the natural order of the sphere, the former's wings being a canvas for intricate designs and patterns as Spring created them. Each creature she created was a work of art in of themselves, if one had the appreciation and ability to see the way their bodies functioned in addition to more cosmetic features.
Summer, eager to populate her realm with beasts suited to her, turned many of her own population of slimes into creatures that could scale the gnarled trees to get to the juicy fruit they bore and glide to another tree using the thermals from thd perpetually comfortable heat rising hot air and the breezes of cooler air to carry them. She gave them scales for protection and deployable sail-like fins to keep themselves cooler by distributing the heat over a wider area. Others slimes were made into taller beasts that could pluck the fruits and feed on the bark of the trees for sustenance, their musculature being lean and meant more for speed and dexterity, with a long prehensile tail that could whip around that ended in a set of pincers that could grab things.
Autumn, focused more on the harvests and the operation of her Sphere than indulging in creative desires, choose to shape her Spirit Beasts into extensions of her Will and commanded them into shapes that would serve as beasts of labor, their forms made for enduring long hours of work and becoming a strange mix of beast and farm equipment meant to plow fields and help to reseed them with a new generation of plants, while their digestive system was made far more robust in order to handle eating any spoiled and rotting plants without worry of sickness. She also made bat-like creatures and birds to move across the sky and act as way to both carry seeds farther and out of sense that the sky should not be so empty.
Winter was perhaps the less dramatic of her sisters in terms of fashioning her Spirit Beasts, creating creatures that could hide in the snow and whose constitution was hardy enough to survive even the deepest of chills and with limbs strong enough to break through frozen soil and ice. She made small burrowing creatures that could dig below the earth in order to reach the hardy vegetables and roots, letting them make tunnels that she occasionally changed so not to cause issues for the world above ground. She made larger beasts, giant bears of white fur that could hide in piles of snow that covered even their distinctive black horn that even the Spirits could not hide with their command over their forms. Indeed, many of experiments involved allowing the natural processes of the Spirit Beasts to occur to adapt to her cold realm, and then simply pushing them further in order to maximize their ability to survive in even harsher variants of her realm.
The Sisters believed this to be enough, until their eldest brother Wisdom came to them and remarked that they should prepare some beasts to act as deterrents should the humans allow themselves to fall to prey to more violent desires and to maintain order. He also remarked that perhaps they should create a Spirit Beast to act as more humanoid avatar for sake of easier communication.
Heeding the wisdom that their eldest brother was named after, the Sisters create a select few creatures that were made not according to individual tastes and desires, but for sake of protecting their future wards from each other should the need arise. Guardian Beasts, made strong, fast, and tough while still trying to maintain at least some aesthetic resemblance to other creatures within their respective Spheres. As for the matter of an Avatar, the sisters simply kept a Spirit Beast in its primordial slime form as a pet on standby, ready to be shaped according to how they wished to present themselves to the humans that would soon arrive.
On a separate note, Spring may have found the original slime form of Spirits Beasts to be very cute, and perhaps has kept more than one in that state for her to dote over.
And thus was the Eden Spheres, the Gardens of Mankind, were made home to both flora and fauna under the command of the Quartet of Seasonal Spirits, each of them eager in their own way to receive their destined wards.
@Dragonofelder