Open the Lid of the Cauldron of Hell: Mabinogion Pseudepigrapha

The stage is England in the 12th century. When the Third Crusade was launched, a boy who is making a living as a gravedigger meets a girl who called herself the "Cauldron of Regeneration." Will she bring rebirth, or destruction—. A full-scale dark fantasy is about to begin.

(Source: Kadokawa, translated)