What is "hortdan"

In Turkic mythology, Hortdan ( Azerbaijanese: Xortdan, Turkish: Hortlak, Tuvan: Хортан) is the troubled soul of the dead rising from the grave. Some Hortdan can be living people with certain magical properties. Some of the properties of the Hortdan include: the ability to transform into an animal, invisibility, and the propensity to drain the vitality of victims via blood loss. Hortdans are also known as immortal vampires.