You are a prominent hellhound keeper. If you purchase the Retainer background you may designate that retainer as a hellhound animal retainer. Additionally, you gain two hellhound retainers instead of one. This is an exception to the rule which requires each Retainer to have its own background. If you spend XP to raise the level of that Retainer, the increase applies to both hellhounds. In addition, thanks to your family’s widespread breeding, if you lose a hellhound Retainer, you regain it one week later.