A vampire is a creature that feeds off of the energy or blood of others. The rune spell known as Vampiric Mark of Striking is said to imbue a weapon with the essence of a vampire. The term "vampiric" is often used to describe artifacts or spells that feed off of blood or drain a victim's lifeforce, such as some warlock abilites. There are spells and items that are said to be vampiric. The nathrezim are often described as being vampiric.
'Vampires' of World of Warcraft are not to be confused with the vampires found in European mythology. As stated above, a 'Vampire' of World of Warcraft is a being or entity that drains the energy, life force, or blood from another being, typically using spells or artifacts. A vampire found in European mythology is specifically a corpse who rises at night and bites humans on the neck using long and pointy canine teeth, and sucks their blood. The latter does not exist in WoW.
In Wrath of the Lich King EditWotLK This section concerns content exclusive to Wrath of the Lich King.
World of Warcraft: Wrath of the Lich King introduced the darkfallen, a race of undead elves loyal to the Scourge, along with death knights, that can also cast spells that could be called vampiric, such as Vampiric Blood. Their leaders display a number of traits associated with the traditional vampire archetype.