Incursion

A movement of one faction or force from one realm to another.

Usually reserved to describe a deliberate invasion or action.

Historically used to describe the appearance of agents of the nothing in our reality - this definition is less relevant in present day due to the Concordian Barrier but still potentially valid.

In modern times term frequently used to describe Fae (and less so other creatures) appearing on Earth Realm via the Otherplace in a variety of manifestations (all assumed to be coordinated resrouce movements to a smaller or lesser degree).