Môrism, also known as Nocturnism, is a sect of Aeterism that was the primary faith of all Drow. They venerate Serenox as the Night Mother, and saw the darkness, the moons, and the stars as sacred. After the goddess' death in the Omniborn Crisis, the faith took a darker turn as its adherents started to mourn the loss of their goddess for eternity. The faith believes that the golden era of the cosmos is over and only eons of darkness and suffering await them, with little hope for a better future. The faith is heavily linked to Pure Dark worship and the Shadowfell as well. Môrism is the state religion of the Mourning Court in Eteru and is centered on the holy city of Mothhai. The Veiled Queen of the Court is considered to be the spiritual leader of the faith, her consecrated bloodline believed to have the last remaining silk weaved by Serenox herself.
Over time, the faith has come to mourn all the innumerable gods who died in the Omniborn Crisis such as Moros, Rhos and Tidāhi in addition to mourning Serenox. A central tenet of the faith is remembering those who are lost to the void and oblivion, and being the last peoples to worship long-dead gods not unlike Elder Gigarion. They still worship and recognize the other gods of the pantheon, and many even pray to deities such as Saenus, Theratis, and Deltus. Staunch worshipers among the Drow maintain vigil, awaiting Serenox's return, holding onto the cosmic threads of hope for her eventual rebirth. There is something primal about the dark, as clerics of Serenox still gain power from her domains to this day despite the goddess being long dead. Theories of where they draw their power from speculate that it could be from the night itself, the darkness, or vestiges of Serenox's soul within Saenus.
Môrists surprisingly do not hold bad views of Saenus despite the fact that she killed Serenox. Since the Night Mother named Saenus as her successor herself, they recognize Saenus' ascension as the last wish of their mother. That being said, they do not believe Saenus to be as strong as Serenox and view the young goddess as barely holding the night together. Deltus is viewed in a negative light in Môrism due to his role in the banishment of the Drow and his opposition to his consort Serenox. While he is still worshiped by farmers and priests for his blessings, the widower Day Father is seen as one who has abandoned them.
The dark worshipers and the unseelie within Môrism hold a favorable view of the Shadowfell and recognise Morgariel as a legitimate dark goddess, despite Serenox's opposition to her and the Night Mother being the one who sealed Morgariel in the first place. While not all Môrists are dark worshipers, it isn't looked down upon by the high priestesses. Môrists vehemently oppose the Triadist belief of Arryestria being a reincarnation of Serenox.
History
The elves who worshiped the Night Mother became increasingly insular over time, and legend whispers that Serenox deceived her devout Moon-Elf adherents into rebelling against the budding Aeteria. For this betrayal, Deltus excommunicated the moon elves who followed Serenox and didn't favor him, and banished them to the Underdark never to see Serenox's night sky ever again and be forever severed from her celestial embrace. The transformation of these Moon Elves into the Drow is shrouded, either seen as Serenox's blessing or Deltus' curse. Serenox is known to have perished at the hands of Saenus during the Omniborn Crisis, when the Omniborn directly tried to challenge fate itself and rewrite the stars in their favor. This unprecedented cataclysm spurred a rare unity between Drow and High Elves, albeit fleetingly, against the common threat. After the war, Saenus was forced to take on the duties and powers of Serenox, and became the new goddess of the night. It's said that this punishment was decreed by Serenox herself who saw the good her killer would do in the future.
The continent of Eteru once had an Underdark like any other land, until part of the surface collapsed into the Underdark during the cataclysmic Omniborn Crisis. This turned much of the continent into badlands, and exposed the drow there to the harsh surface. Their society, known as the Mourning Court, developed a new culture of venerating the moons and scorning the sun. Despite their reputation as reclusive and insular people who practice dark magic, the sunless drow are obviously not inherently evil. They value community and cooperation, and work together to protect their newfound lands and traditions. While they do venerate spiders, they do so simply as a lasting remnant of the wider Drow culture that persisted in the ancient times.