The New Religion were the practices and customs that the kingdom of Camelot followed after the fall of the Old Religion which was ruthlessly attacked by the tyrannical King Uther Pendragon of Camelot.
Merlin the man destined to allow the Old Religion to co-exist with the New Religion
It was unknown as to what the New Religion dictated but the great sorcerer Merlin was intended to revive the proceeding Old Religion and allow it co-exist peacefully with the New Religion as part of his great destiny.
The Old Religion fell after it was attacked by Uther Pendragon due to the death of his wife, Ygraine de Bois by the malpractice of magic by his once trusted friend the High Priestess Nimueh. The peaceful but later corrupted Old Religion in Camelot was destroyed after a desperate Uther asked a favour to use magic to give his barren wife a son to secure the Pendragon line, this resulted in the birth of the once and future King Arthur
Nimueh claimed that the death of someone in exchange for creating a life was necessary to protect the balance of life and death in accordance with the ways of the Old Religion.
Morgana Pendragon, a follower of the Old Religon
Uther, therefore, blamed all magic for his wife's death and carried out terrible retribution against its practitioners. While some followers gave up using magic or pretended to have given up using magic, such as Gaius who conformed to the New Religion, others refused to convert. This led to the execution of probably thousands of followers of the old ways in a horrific programme known as, 'The Great Purge'.
Notable victims of the purge were Gregore and Jaden, friends of Gaius who practised black magic, who were the parents of Edwin Muirden, it also led to many seeking retribution against Camelot and notable individuals were the High Priestesses Morgause and Morgana along with many others.
Following the Great Purge, Uther banned all forms of magic in Camelot (The Dragon's Call) and issued the New Religion as the new customs of Camelot, however, Camelot still followed druidic or Old Religion-related festivals like the Feast Of Beltane and Samhain Eve.
During Samhain, the people of Camelot would prepare a feast to mourn their deceased and those who had departed this life. The feast would be preceded by a speech from the current ruler before a toast, as for the Feast of Beltane which celebrated the end of the Dark Season, Camelot would also hold a traditional hunt as Arthur told Princess Mithian before the feast and it would be a joyous celebration.(The Hunters Heart).