The Lambs of Dalamud
Near the end of the Sixth Astral Era, following the Garlean Empire making contact with Dalamud, the satellite began to slowly descend towards the realm of Eorzea. For millennia, the people of Eorzea believed it to be a lesser moon, even worshiping it at times through history. Of those who worshiped the lesser moon however, none were as fervent as the Lambs of Dalamud. When the moon began approaching, this cult viewed it as a deity in some form or another, and its approach as a sign of their deities' return.
The inner workings of the cult are unknown, as any taken in by the Lambs of Dalamud do not often return. It is unclear if the Lambs were seeking to resurrect their god, or harbor goodwill from it when the moon touched down, or if the moon itself was the god. The prevailing belief is that by offering blood to the moon, Menphina would send her warbeasts to the land and purify it, then reach down to the Seventh Hell and resurrect its followers. Whatever their intentions, the Lambs of Dalamud slowly began appearing in every shadowy corner of Eorzea, and became known for kidnapping the unwary and sacrificing them in bloody rituals at Gwyr-Aen.
During the events of the Battle of Carteneau, the Lambs of Dalamud were continuing to make sacrifices until the satellite detonated in the sky and Bahamut was set free. Witnessing the destruction of the "moon", the Lambs of Dalamud became enraged and blamed the "heretics", anyone not within the cult, and swore revenge against them all.
Following the aftermath of the Seventh Umbral Calamity, the Lambs flooded into the Tam-Tara Deepcroft, using the buried there as bodies for Voidsent to inhabit. Fearing the repercussions of this, the Wood Wailers hired adventurers to head in and dispatch the Lambs. Many of these parties were met with demise, such as the party of Edda Pureheart. Eventually the ambitions were put to rest when the Warrior of Light entered the deepcroft and slayed the resurrected Galvanth, whose body was given over to a Soulflayer Voidsent and drove the Lambs out.
The Lambs of Dalamud also managed to break the barriers on the Amdapor Keep that was raised by the Elementals to prevent any from entering the ruins and obtaining knowledge of forbidden magicks. They used the Keep as their stronghold, and the knowledge within to attempt to bring back their god via magicks and blood rituals. Again, the Warrior of Light ended their plans by storming the ruins and slaying the Voidsent they had called upon. Since this the few remaining Lambs of Dalamud have gone into hiding, and there has been relatively little activity or movement from the cult.