The tribe was, in essence, a group of Cainites (mainly rogue Assamites), centered around the Weeping Master and his disciple Anosh. These Cainites found an ancient and mysterious valley in which stood the Weeping Stone.
This stone cried drops of blood which filled the drinker with sorrow, rage, and regret. The Weeping Master believed that this stone was the petrified Zillah, preserved by Caine after she had witnessed the slaughter of her brethren by the unfaithful Third Generation. The Lost Tribe believed that by drinking the blood they severed their ties to the cursed Antediluvians and instead formed a covenant with Caine himself. During Gehenna they would be destined to stand by his side and his judgement of the Antediluvians and their progeny.
The apocalyptic message of the "Black Hand" resonated within the nascent Sabbat and the Black Hand joined the rogue Anarchs a short time after the Convention of Thorns, serving as a semi-independent sub-cult within the sect that acted mainly as assassins.
Unbeknownst to them, another much older sect had begun to infiltrate the ranks of the Black Hand, until half of the highest Seraphim had forsaken their original mission for the goal of the "True" Black Hand: serving the Antediluvians during Gehenna and to propitiate them by sacrificing their ill-begotten progeny.
As the methods and goals of both sects seemed to mirror each other closely, few amidst the sect suspected about this infiltration until many of the Hand who had been secretly part of the True Black Hand – including two Seraphim – suddenly vanished after the first spirit nuke hit their hidden headquarters in the Shadowlands during the events that lead to the creation of the Sixth Great Maelstrom.