Clerics transformed into the most hideous beasts.
The Cleric Beast, like those that came before it, is a Cleric of the Healing Church who has given over to beasthood completely. Ludwig was the first of many Healing Church hunters to come, many of whom were clerics. As it was, clerics transformed into the most hideous beasts.
Seeking a way to become more than human the scholars of Byrgenwerth discovered old blood within the chalice dungeons below Yharnam. The discovery of blood made their dream of evolution a reality. Metamorphosis, and the excesses and deviation that followed, were only the beginning, however, the discovery of blood also entailed the discovery of undesirable beasts. Because of this the discoveries related to beasthood were deemed forbidden, as seen in the description for the Beast Caryll rune, and the discoveries were likely forbidden by Willem. Many of the students at Byrgenwerth however, did not agree with Willem in his views on blood and wished to continue studying its effects. These events led to the schism at Byrgenwerth where many of the students departed the institution, including Laurence, who would go on to found the Healing Church.
Members of the Healing Church continued to study the old blood, and would partake of it in a ritual called Communion. Vicar Amelia is found repeating a mantra that seemingly represents the teachings of the Healing Church members:
Seek the old blood.
Let us pray… to partake in communion.
Let us partake in communion… and feast upon the old blood.
Our thirst for blood satiates us, soothes our fears.
Seek the old blood… but beware the frailty of men.
Their wills are week, minds young.
The foul beasts will dangle nectar and lure the meek into the depths.
Remain wary of the frailty of men.
Their wills are weak, minds young.
Were it not for fear, death would go unlamented.
Amelia's mantra illuminates a number of key points. Members of the Healing Church would feast upon the old blood. Drinking the blood satiated a need or desire within its members, driving away their fears. But there was always an inherent danger in partaking of the old blood. Members understood that mankind was frail, that their willpower is weak and their minds young, especially in comparison to more advanced beings like the Great Ones. When partaking in blood, there was always the temptation to embrace beasthood. The Beast Roar description indicates that beasthood lurks deep within the frames of men, a nectar luring the meek into the depths. This beastly nature offers strength, relief from all fear, but it comes at a high cost.
Laurence, first vicar of the Healing Church became the first cleric beast. And it seemingly was not long before others joined him. Brador, a Church Assassin and hunter killed his compatriot after they transformed into a Cleric Beast, skinning the beast thereafter and wearing its hide as testimony of what he had seen and done. He brought this testimony to the Healing Church, who swore him to secrecy, providing him with a soundless bell of death that would allow him to keep their secrets.
But this secret, like the beasthood within mankind, could not be contained so easily. When clerics began transforming into unspeakable beasts, the Church needed something to retaliate with. Weaponry and techniques were developed to deal with Cleric Beasts. One example of this is the golden radial blood gem, kept for generations within the Church that strengthens attacks against those afflicted intensely by beasthood.
Perhaps across these generations the Church searched for a cure to the beasthood that plagued them, but like Brador's compatriot, our Cleric Beast serves as testimony to the Church's failure.