- “As Neanderthals are to human beings, the Turok-Han are to vampires. They're a primordial, ferociously powerful killing machine, as single-minded as animals. They are the vampires that vampires fear. An ancient and entirely different race, and until this morning, I thought they were a myth.”
- ―Rupert Giles[src]
They are a race of ancient powerful vampires stronger and fiercer than the regular vampires. Judging by Giles' description of them, they are monsters even amongst vampires.
They are also resistant although not invulnerable to being staked through the heart, requiring to be impaled rather than merely stabbed. They are also vulnerable to beheading, sunlight, and holy water, though crosses do not affect them whatsoever.
The First Evil, via its Bringers, first used Jonathan Levinson's and Spike's blood to open the Seal of Danzalthar which released the first Turok-Han. Buffy's first encounter with the Turok-Han nearly killed her; however, she managed to kill it during their second fight.
They were given the nickname of Ubervamp by the Scooby Gang more specifically Anya. 'Uber' was first commonly used by German philosopher Nietzsche who coined the phrase 'Ubermensch' - which referred to the higher state that man may aspire to. Ubervamp is, therefore, a reference to the higher state which vampires may aspire to.
The performance of the Turok-Han army is far poorer than the first one in the series. While the first Turok-Han was nearly unstoppable, forcing Buffy to use every possible resource to defeat it, the newly-activated Slayers (and even the non-superpowered human members of the Scooby Gang, like Xander and Dawn) were able to defeat them with relative ease. In the audio commentary for the episode Chosen, Joss Whedon explained that he is aware of the continuity issue with the Turok-Han's powers, and explained that the story behind the season/episode he wanted to get across to viewers was more important than the continuity.