In the movie, there's some dialogue between John Carter and Matai Shang, where the latter elaborates a little on the reasons they do what they do. I didn't get it, though. When asked by John Carter about their cause, he says they have none, but still for some reason have an agenda, and all their machinations, the wedding and giving the ninth ray to Sab Than, fits into it. Then he says:

We don't cause the destruction of a world, Captain Carter. We simply manage it, feed off it, if you like. But on every host planet, it always plays out exactly the same way. Populations rise, societies divide, wars spread. And all the while, the neglected planet slowly fades.

What does he mean with 'feed off it'? Seems like their motivations are to direct civilization in a way to minimize ecological damage?

  • 2
    I wish there were a good answer to this, but it's just one of the many nonsensical changes they made in the translation to film. I got the sense they were setting it up so the Therns would be a greater enemy later, perhaps in the sequel, which is where they first appeared in the book.
    – Tango
    Commented Aug 26, 2013 at 6:31
  • I hate how they changed the story from the book, planned the movies as a trilogy and then only shot one of three. So yeah, I'd say wait for the sequel to get your answers, but it probably won't come... Commented Apr 23, 2014 at 17:25
  • I got the feeling that since the books are public domain, there were a lot of different scripts floating around, and they just smashed several of them together.
    – KSmarts
    Commented Apr 21, 2015 at 18:53

4 Answers 4


If you had read the next book following the princess of mars i.e. the gods of mars, therns are humanoids which have perpetuated a false religion in which they claim that their queen Iss is the mother of all races and one must journey south for salvation. When tharks and other men(red men) complete this journey, they are killed and fed upon by therns and their creatures (plant men). Thus, this journey is considered the final one and no one returns back. By maintaining this false supremacy, they get unlimited supply to food and exclusive access to the south polar region where the only sea of mars exists(in that world). The books just describe john carter on mars as an astral projection of him on earth and therns are no more super natural, just those with a false sense of supremacy.


It has been years since I read the Princess of Mars series, but I don't recall the Holy Therns having any such powers. They were the centre of the Barsoomian religion and quite fanatic about it. In effect the demons of hell.

This other thing is a figment of Hollywood writer's imagination.


I took it that they were vampiric in the sense that they feed off the negative energy of a world's destruction.

  • Welcome to the site. Do you have any references that support that opinion?
    – Stan
    Commented Aug 26, 2013 at 13:22
  • 3
    This isn't supported by anything in the first three books, and I don't recall anything of the sort in the movie.
    – phantom42
    Commented Sep 25, 2013 at 13:51
  • What does that even mean? "Negative energy" isn't a real thing... Commented Oct 22, 2014 at 7:40
  • 1
    @ValekHalfHeart - not according to "Ghostbusters 2".
    – Omegacron
    Commented Nov 21, 2014 at 16:27

I took it to be that they took advantage of the chaos of a decaying planet, mostly through looting.

  • 4
    Welcome to the site. Can you provide any further info to substantiate this answer? As it stands it's quite low-quality; some citations from canonical sources that provide evidence for your reading would greatly improve it.
    – user8719
    Commented Oct 21, 2014 at 22:44

Not the answer you're looking for? Browse other questions tagged or ask your own question.