Ley lines are often described as invisible currents of magical energy that flow through the earth and can become visible in the sky under specific conditions. In the world of Critical Role's Exandria, the normally invisible ley lines became visible during the apogee solstice of 843 PD, appearing as glowing, aurora-like streams twisting through the skies.

These visible lines were not static; they shifted and reshaped, creating dangerous phenomena such as arcane windstorms and psychic static.

The visibility of these lines is tied to celestial events, with the solstice being a key trigger for their manifestation.

The perception of ley lines in the sky is not universal. Some believe the visible streams are not the lines themselves but rather an interaction between the ley lines and other forces, similar to how solar winds interact with Earth's magnetic field to create the aurora borealis.

Others suggest that ley lines exist both in the ground and the sky, being a layer of magic that permeates the world, with their visibility depending on the observer's sensitivity and the time of year.

In some interpretations, the lines are seen as a network of energy that converges at nexus points, which can be located in the sky or on the ground, and are often associated with powerful magical sites.

In other fictional universes, such as the Rifts setting, ley lines extend vertically into the sky, reaching up to half a mile above the surface, and underwater leylines extend about 1.5 miles upward from the seafloor.

This suggests that the concept of ley lines in the sky is a common theme in fantasy and science fiction, where they are often depicted as visible, dynamic energy flows that can influence the environment and magic. wiki