Eart Soul Orbs, also known as ESO, are items that can be used to level up your sperion. Leveling a sperion
Stack of ESO
makes it more powerful and also allows it to be morphed by using soul prints and purified crystals once it has reach a high enough level.
It takes 25 sperion to increase the sperion experience once, and each experience increment is about half the level up bar.