Not precisely allies or contacts, your retainers are servants, assistants or other people who are your loyal and steadfast companions. Many vampires' servants are ghouls (p. 275) - their supernatural powers and blood bond-enforced loyalty make them the servants of choice. Retainers may also be people whom you've repeatedly Dominated until they have no free will left, or followers so enthralled with your Presence that their loyalty borders on blind fanaticism. Some vampires, particularly those with the Animalism Discipline, use "hellhounds" (ghouled dogs) or other animal ghouls as retainers.
You must maintain some control over your retainers, whether through a salary, the gift of your vitae or the use of Disciplines. Retainers are never "blindly loyal no matter what" - if you treat them too poorly without exercising strict control, they might well turn on you.
Retainers may be useful, but they should never be flawless, A physically powerful ghoul might be rebellious, inconveniently dull-witted or lacking in practical skills. A loyal manservant might be physically weak or possess no real personal initiative or creativity. This Background isn't an excuse to craft an unstoppable bodyguard or pet assassin - it's a method to bring more fully developed characters into the chronicle, as well as to reflect the Renfieldesque followers for which the Kindred are notorious. Don't abuse it.
1 - One retainer
2 - Two retainers
3 - Three retainers
4 - Four retainers
5 - Five retainers