Oversoul is the function of being able to integrate one's spirit ally with a physical medium of some kind and infuse it with mana to allow the shaman to manifest and manipulate the spirit ally (as opposed to the spirit ally manipulating the shaman) into some kind of fighting force. whether it be a weapon, armor, or a fighter. This is a mode of the spirit ally & the shaman achieve by using a medium that represents the spirit and is only sustainable with mana, increasing the amount of mana an oversoul has increases its size (note every spirit ally has a set limit as to how much mana is needed to control them via integration or oversoul). In oversoul mode the spirit ally as an oversoul can interact with the physical world due to the medium representing it and giving the oversoul its characteristics and the mana fleshing it out.