Vrah's dead sister, on whose grave she intends to mount Carl's head so she can feast on him in the afterlife.
Named only in Vrah's Note, Vrah's sister is dead and buried somewhere Vrah calls home. Vrah's threat to Carl closes with her promise to take his head there and place it upon her sister's grave, so that the sister may feast upon him in the afterlife.
The detail turns the hunt personal: whatever Carl did or is thought to have done, Vrah frames his death as an offering owed to a specific dead woman rather than as sport or contract.
The dead relative whose memory drives Vrah's vendetta against Carl.