Q: What are the Holy Therns in "John Carter"? In John Carter 2012 movie, there was those super bad guys who can shape-shift and teleport. According to them, they are immortals, but :

 John Carter kills 2 of them

According to the cast section of Wikipedia article of John Carter their name is "the Holy Therns". Who are they? Terran? Martian? Gods?

A: The Holy Therns are a species who don't show up until later in the series. They are revered as essentially gods to the red and green men of Barsoom. Their skins is white and they have blonde hair (which for some reason I remember being a wig).
One would best compare them to the Gods of Olympus as they lived in a place where the red and green men believed to be holy and where you would go to die. It's basically a forest and mountain far off from where the red and green men typically inhabit.

Carter and Tars Tarkas encounters them  in the second and third books of the series where they learn that the horrible truth about the Therns in that they merely trap those who come into their land to die as slaves and that they essentially control the great white apes.Their teleportation, in the books at least, is revealed to be a trick of shadows, hidden passages and I believe mirrors. The immortality is a superstition tied to their being seen as supernatural. Of course, Carter and Tars Tarkas quickly learn that they can be killed just as anyone else and that the only real difference between the Therns and the red/green men - and later the black men - is skin color. 


A: when the John Carter book refers to immortals it means that no-one dies of old age upon Barsoom and potentially can live forever, though most die by the sword on such a warlike planet.
On Barsoom when someone reaches the age of one thousand they take the journey down the river Iss an underground river which all Barsoomians believe leads to Paradise. However its far from Paradise, the survivors of this arduous journey find themselves in a valley ruled by the Holy Therns (who often travel among the people of Mars to foster this believe on the outside world)
The survivors are either set upon by Great White Apes and Plantmen for the entertainment of the blood thirsty Therns or are taken as slaves to serve the Therns for a one year period before ending up on the dining tables of said Holy Therns
