The Late Night Expansion Pack
In order to become a vampire, you must have "The Sims 3: Late Night," the third expansion pack of the series, installed on your computer. As in the case with "The Sims 2: Nightlife," the expansion pack adds an element of nightlife to the base game. In addition to the nocturnal vampire, which serves a much more developed creature in "The Sims 3," "Late Night" adds nightclubs, high rise homes, celebrities and dive bars. Those who have played "The Sims 2: Nightlife" and "The Sims 3: Late Night" will note that the vampires are decidedly different. In the former version, vampires took on a traditional stereotypical feel, with capes and fangs to match. In "The Sims 3," vampires are modern, wear traditional clothes, and have less obviously pale skin.
Becoming a Vampire
In order to become a vampire in "The Sims 3," you must ask another vampire to turn you. Because this is a social request, the initiating Sim must have a relationship with the vampire; otherwise he will take offense and reject you. A minimum relationship of friend is required for the interaction to be successful. Once you have been turned, you must work to sustain the life of the vampire, more than was required in the previous version of the game.
Sustaining the Life of a Vampire
Once a Sim becomes a vampire, the Sim's needs will change to reflect this. Hunger on the Sim's need bar will be replaced by Thirst, a thirst that must be quenched with blood. To quench thirst, a Sim may do three things. She can drink plasma juice, available for free to a vampire from any fridge; she can plant, grow and eat plasma fruits; or she can feed on Sims. Vampire Sims can hunt for prey, but must have a minimal relationship before they can bite. They are not required to be friends, but prior successful interactions are usually necessary, as the Sims must have an LTR or lifetime relationship of at least 20. The type of bite a vampire can take will depend on the relationship between the two. Vampires can never feed on parents, children or pregnant Sims.
Caution
There are several elements within the game that can serve to harm your vampire Sim. Sunlight lasting more than a few minutes will scorch your Sim, and rid him of vampire powers for two days. Garlic will make your Sim nauseous. Mating with a non-vampire Sim will yield a 50 percent chance that the resulting child will be a vampire as well.