From itch.io:
Inspired by English magical folklore surrounding the Society of the Horseman's Word.
The production of this magical relic is a secret closely guarded by the Sodality of Bestial Whispers. Used in conjunction a throatily rasped utterance of the sacred word ‘ONE’, this enchanted toad bone makes any animal it touches devoted to the wielder - although great skill is required to execute the enchantment.
It seems the original intention of the Bone of Batrasaxas was for animal husbandry - to tame horses, and so forth… Later, members of the Sodality realised that it also worked on humans. Rogue Sodalites became corrupted by the power of the bone. Some enslaved the farmers who once employed them, some dominated and manipulated lovers, while others even enchanted whole villages, making themselves objects of devotion to fanatical cult devotees.
Includes: Background and rules for using the Bone of Batrasaxas; Stats for Yelga, Maistress of the Sodality.