All things are animated by spirit (literally anima = spirit). The greater the thing the greater the spirit and the lesser the thing the lesser the spirit.
When you see a blade of grass move in the wind, that is because the spirit of the blade of grass is being tickled by the spirit of the wind.
While the blade of grass exists, its spirit is tightly bound to it and not easily moved to animate something else, but countless blades of grass are being eaten by countless roltons all the time, and their spirits are set lose and wander until something new catches them and they animate it.
This may be a new blade of grass, or a wisp of wool on the back of a rolton, or they might be caught by the magic of a spiritualist and animate a spell. Just as there are countless blades of grass, so there are countless unattached spirits that can be harnessed by those with the skill to do so.
