Selune

Selune is a goddess so closely associated with the moon that her name has become the common word for that celestial satellite orbiting Faerun. As the Moon goddess, her power is said to wax and wane with the phases of the moon, with her influence been most strongly felt on the full moon, and reducing to the scale of a lesser deity at the new moon. Selune is associated with moonlight, twilight, dreams, stars, feminine power and a woman's monthly cycle, and sleep, but also therianthropy and madness.

Origin

Selune's origins are part of the creation story of faerun. It is said that early in the creation of the Realms, matter on the material plane separated itself into darkness and light, and two powers, Shar and Selune arose from them. They were sisters, reflections of each-other, and together they fashioned Toril and other celestial bodies out of the primordial chaos. Chauntea arose as goddess of the soil and rock of Toril.
Chauntea asked the sisters for warmth and life to be brought to the worlds. Shar, the goddess of darkness refused, while Selune of the light wished it to be so. They fought, and for a long time their war shaped the Realms. Gods of fighting, magic, disease, life, murder and death came into being from that war, and eventually Selune siezed an opportunity. Reaching into the plane of fire, she pulled some of it into the sky to become the sun, burning and weakening herself in the process. However, it was something that Shar could not undo, and thus warmth was brought to the Realms and life sprang into existence on Toril and the other worlds.
Shar's empty darkness was kept at bay, and Selune's power grew and lessened with the turning of the spheres, while Chauntea became protector and mother of this life and nature blooming on Toril.

Therianthropy and madness

Selune's divine portfolio includes were-creatures and shapeshifters. Most therianthropes are able to access their full power only on the full moon, and many good-aligned were-creatures are attuned to this goddess. On the other hand, Selune's power can be used to suppress the effects of lycanthropy and other therianthropies, and blessed silver is a weakness of theirs through Selune.
Selune might punish transgressors with temporary insanity or 'lunacy' changing their perceptions of reality into a dreamlike state, where their subconsious drives and desires come to the surface. In some cases she is prayed to for relief from madness, or for insight into it's cause and treatment or resolution.

moonlight and dreams

Selune's aspect of moonlight, suggests many creatures associated with her might have darkvision or greater visibility in dim light. Her followers perform their rituals at twilight or under a full moon. She is also associated with sleep and dreams, and can communicate or allow communication through dreams.

Sehanine Moonbow

Among the various pantheons, Selune's elvish counterpart, Sehanine Moonbow, is generally considered to be alternative names, rather than one being an aspect of the other. Elf werewolves were known as Lythari, and were much more in control of themselves and their shapeshifting power. They did not have a half-shifted form, and were generally good aligned and attuned to nature.