Ghoul

In Vampire: the Masquerade and Vampire: the Requiem, a Ghoul is a human granted supernatural powers by drinking Kindred blood. The bulk of this article covers Ghouls from VtM.

Creation
Ghouls are created when a vampire feeds at least one blood point worth of blood to a mortal, whether that person is a human or an animal. As long as the blood remains in the system, the character is ghouled. Under normal circumstances, the blood will remain in a mortal's system for about a month, after which they must acquire another blood point to maintain the benefits.

Ghouls are created by Vampires for a variety of reasons; most Vampires use them for daylight service or to acquire a particular set of skills they do not possess. It is not uncommon for Elders to ghoul a computer expert, banker or chauffeur in addition to the more traditional bodyservant. Because ghouls become subject to a Blood Bond fairly quickly, they are considered to be trustworthy servants.

Domitors in the clans treat ghouls poorly in different ways. The Lasombra use them primarily as bodyservants since Lasombra have trouble grooming themselves; this is usually a short unhappy lifestyle. Tzimisce use ghouls for experiments and art, while the Assamites and Giovanni tend to ghoul prospective candidates for the Embrace. Camarilla clans generally use ghouls as servants, and are far more prolific with them than the Sabbat are.

Humans and animals can be ghouled, the Nosferatu have a particular preference for animal ghouls and tend to build ghouling stations called Spawning Pools. Nosferatu communally bleed into a small pool of water which animals then drink from and become ghouled.

Benefits
Ghouls are immortal, as long as a ghoul has access to vitae, they do not age. In addition, they can heal damage using blood and learn Disciplines, although at a steep experience point cost. Ghouls also receive a point of Potence for free.

Disadvantages
Ghouls are subject to a weaker version of frenzy.

All of the advantages of ghouling go away without vitae in the system. The older a ghoul is, the faster it needs to get vitae before damage kicks in - ghouls over a certain age will crumble to dust the instant they run out of blood. In addition, vampiric blood is highly addictive, Ghouls who try to voluntarily kick the habit will lose all of the advantages of vampiric blood and experience painful withdrawal symptoms.

Ghouls are generally blood bound to their domitors very quickly; some domitors will constrain the ghoul until the bond is formed. Ultimately, ghouls are slaves to their vampire masters.

Miscellany
Animal ghouls tend to mutate the longer they have been exposed to vampiric blood, becoming larger and fiercer. Blood addiction is just as strong for ghouled animals, eventually reaching the point where even vegetarian animals (such as sheep) will hunt for blood due to their hunger for it.

Ghouls can breed ghouls; although the process is extremely uncertain, ghoul families (Revenants) which make their own weak vitae internally have been around for millennia.

Differences Between VtM and VtR
In VtR ghoul creation requires expending a willpower point per month, either by the ghoul or the domitor.

Reference

 * Ghouls: Fatal Addiction Major VtM sourcebook on ghouls and ghouling.
 * Ghouls Hardcover sourcebook on ghouls in VtR.