Vampires have existed in previous parts of the Elder Scrolls series. There, players had to fight against a vampire and often let themselves be hit by it. With every hit, there was a 10% chance of being infected with “Sanguinare Vampiris,” a disease that gradually turned the player into a vampire – unless cured at a shrine.
2017 Update: ESO Guide: Becoming a Vampire – Spawn Points and Quests
If the disease was not cured within 3 days, the player themselves became a bloodsucker and was thereafter avoided or feared by their fellow humans. Furthermore, they had to quench their thirst by breaking into houses and draining the blood of innocent citizens. If they did not do this, they had to live with negative effects, such as reduced health. However, there were also advantages to increasing blood thirst. Although the body became weaker, the abilities became significantly stronger.
In The Elder Scrolls Online, vampirism functions similarly. As with werewolves, there are rare vampire groups in the game that can infect the player with vampirism. This also brings some disadvantages, but also access to a new skill line.
More information about how to become a bloodsucker can be found in the new episode: Interview with a Vampire.