When the entities first came to earth they set loose millions of shards, each on its own precisely calculated path to a host. Each path narrow and perfect, no two intersecting or colliding as they spiral through a multitude of dimensions.
Normally this storm whirls on without any accidents, despite its vast complexity. However, normally no one is shooting through dimensions at an entirely orthogonal direction from any these shards had seen. Why, if that were to happen there'd almost certainly be a -