Well, simply put the heartstone (with 2 dots) gets access to abyssal familiar (1 dot) background in function wise. The familair obeys and follows person who has the heartstone. But optionally person can form a actual real familiar relationship with the ghostly entity (simply said purchase the background). Then heartstone would not provide familiar but rather empower basic familiar someways.<br/><br/>But I can writer longer write up and write on black and white what benefit heartstone would give to owners of familiars (when it's not providing one to someone who does not have ghostly familiar).