This is Finnlay Kelly
A Yharnamite. Originally following the Healing Church before the scourge came.
That's when he started following the cult that branched off the church. (Same as @voidcreations made)
He is just a layman, but climbed the ranks in the cult. And had a successful controlled turn to beasthood. His self almost entirely intact.
He has the beast rune (maybe other runes as well?) Carved into his body.
Would eat an entire family Suspicious Beggar style.
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He is a sworn protector of any Cult priest or priestess.
But is dedicated to one in particular, Eden Sutton.
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Eden is a priestess within the cult who has taken on a different mission. She calls herself a mender. And aims to aid the beasts of Yharnam big and small.
The cult finds her work honourable and assigned her protection in the form of Finnlay Kelly. Finnlay volunteered to partner with her.
Any beast he can run down she examines. Tends for and sometimes even feeds if they've been lucky with hunts.
A vial of her blood may be given those in grave condition. But she can only spare one vial every so often.