Fairies

The many types of fairies of the world tree appear to be transient folk. Their enticing feast fires are built upon the drifting seeds and pollen of the tree. With little risk to the fairies themselves, they drift downwards as they endlessly dance and party. When a debauch of fairies gets too close to the roots of the tree, they simply fly back upwards, setting new dancing grounds on a suitably convenient new seed.