Shar, the Mistress of the Night, is the goddess of darkness and the caverns of Faerûn, as well as a neutral evil greater deity. Counterpart to her twin, Selûne, she presided over caverns, darkness, dungeons, forgetfulness, loss, night, secrets, and the Underdark. Among her array of twisted powers is the ability to see everything that lay or happened in the dark. Shar’s symbol is a black disk with a deep purple border. Shar was also the creator of the Shadow Weave, which was a counterpart and attack upon the Weave, controlled by the Mother of All Magic and her successors, before both of the Weaves fell into ruin during the Spellplague.
History
Shar and her sister Selûne coalesced out of the material of Realmspace after it was created by Lord Ao. 
They were incredibly close at first, so much so that they believed themselves to be the same being. They worked together to create the heavens and the planets, and then created Chauntea to embody the planets and infuse them with life. Selûne lit the worlds while Shar coated them in shadows. Chauntea, however, claimed that Selûne’s light was not enough for life to thrive like she wanted it to, and begged the sisters for warmth. Shar and Selûne argued for the first time–Selûne wanting their realm to be filled with more life, while Shar was happy with the state of things as they were. The two quarreled violently, creating the gods Targus, Moander, and Jergal in the aftermath. At an impasse, Selûne reached into the Plane of Fire and pulled the largest of the planets into Realmspace where she set it alight, creating the sun. Shar attacked again, and tried to smother the flames, but Selûne tore off a part of her own body and hurled it against her sister. The raw magical power of Selûne’s body punched a hole through Shar’s, and out of the two chunks of their bodies, Mystryl formed. Mystryl aligned herself with Selûne and, outmatched, Shar fled, vowing revenge against them both.
Shar brooded for aeons, striking against her sister and the goddess of magic whenever she saw the opportunity. For roughly the next seven centuries, Shar quietly worked against her rivals and nurtured the Shadow Weave, until Ao forced her avatar to Toril during the Time of Troubles. Shar’s power increased when she killed Ibrandul, though she lost the opportunity to also kill Sharess, whom she had been slowly corrupting. Nevertheless, in the wake of the Godswar, Shar was revitalized in a way she hadn’t been before, and began actively subverting Selûne and the new goddess of magic Mystra. Shar eventually made allies of Bane and a patsy of Cyric in 1374 DR. The Church of Shar attempted to wrest control of magic away from Mystra through various means, including aggressive expansion of the Shadow Weave. Many of Shar’s plots were defeated, but she did absorb most of the divinity of her son Mask, increasing her strength. Eleven years later, Mystra was dead at Cyric’s hand and Shar increased the power of the Plane of Shadow by absorbing the Negative Energy Plane, to create the Shadowfell, where she has ruled over darkness ever since.
Divine Relationships
The creation of the Shadow Weave made Shar the eternal enemy of the goddess of magic, Mystra. This resulted in the brewing of a terrible war between these two powerful deities, that continues to this day. By her very nature, Shar is opposed to powers of light, the unsecretive Shaundakul, and her own sister, Selûne. While she was able to coerce Cyric into his attempted assassination of Mystra, Shar’s only frequent ally is Talona.
Church / Worshipers
The worship of Shar has occurred ever since mortals first appeared on Toril. In addition to her clerics, Shar is worshiped by the shades of Thultanthar and many evil wizards. After Shar’s acquisition of the cavern portfolio from slaying Ibrandul during the Time of Troubles, she gained the worship of subterranean beings such as goblins, kobolds and troglodytes.
The Church of Shar is an organization dedicated to spreading the dogma and carrying out the wishes of the deity Shar. Although all worshippers of Shar can loosely be deemed members, its true membership consists of the clergy of the church. The faith is forbidden in many areas of Faerûn and this leads the church underground, practicing in hiding much of the time. An element of fear is associated with the worship of Shar, since many of her followers are willing to give their lives in her service.
The clergy of the Church of Shar use corruption and subversion to spread Shar’s faith, but they must do this in secret in many places due to the religion being forbidden. The atmosphere of the organization is one of unwavering faith to its leader, Shar herself. Disobeying an order usually results in death. Although devotees are perfectly willing to give their life for Shar, she often does not intend for this to happen because it will deplete the number of her dedicated followers.
The clergy of the church will travel in small groups or individually throughout Faerûn, often disguised as merchants or pilgrims to avoid detection. Their missions usually involve either espionage or murder.