The Cult of Yore is a secret guildless group on Ravnica who keeps old tomes recalling the days before the Guildpact. They converse with those old enough to remember those days and they perform the celebrations and rituals described in those old books. The Cult believes that there is a lack of humanity in the world of Ravnica, that the common folk has had it beaten and bred out of them, and that it is the direct result of the Guildpact.
The Guildpact, according to the brothers and sisters of Yore, created false gods, among them the Ghost Council, the Firemind, the angels of Boros, the Chorus, and the Demonlord. However, the Cult of Yore also believes that change is soon in coming, for the old gods are returning. These old gods are the embodiment of the world's vastness, diversity, unpredictability, wonder, and complexity. They are the Nephilim.
In a world where the routine is the norm, this heralds significant change and the Cult of Yore is excited to see it happen.