Apathetic bloody planet, I've no sympathy at all!!
~ Prostetnic Vogon Jeltz's speech to Earth.
Prostetnic Vogon Jeltz is one of the two main antagonists in the Hitchhiker's Guide to the Galaxy series (along with Gag Halfrunt), appearing in three of the novels. He is the leader of the Vogons, an evil alien race who seek to destroy the Universe.
He and Gag Halfrunt are the overarching and main antagonists of the radio series. He also appears as the secondary antagonist of the first novel as well as its 1981 TV adaption and 2005 Disney/Touchstone film adaptation, a supporting antagonist in The Restaurant at the End of the Universe and the main antagonist of Mostly Harmless.
Prostetnic Vogon Jeltz is described to be unpleasant to look at; even for Vogons. Normally he never smiles, even when he is happy. He will occasionally twitch his cheek muscles to remind himself how it is done but never smiles voluntarily. He is more callous than his people and will happily destroy entire planets and wish that someone will come and yell at him to remind him it's evil so Jeltz can yell back at them and feel better.
Jeltz is a source of fear for other Vogons and Vogons do not want to deliver bad news to him. Jeltz is also not too bright; he just hears "a personal friend" somewhere and decides to try it out, Halfrunt says "No, in my profession we do not make friends."
The Hitchhiker's Guide to the Galaxy
In the first book, Prostetnic Vogon Jeltz is the one who orders the destruction of planet Earth. He is revealed to have moved slightly beyond his ordinary work by blowing up a planet. Jeltz orders the demolition rays to be launched and does a callous goodbye speech to humanity saying that Earth is stupid. Jeltz then blows up the planet and flies off into space on his ship, unaware that he picked up two hitchhikers - Ford Prefect and clueless Arthur Dent, last survivor of planet Earth.
He finds out about the intruders soon enough however, and he tortures them by reading them Vogon poetry, the third worst in the Universe. Jeltz reads a special torturous poem of his own devising, which goes like:
Oh friggled gruntbuggly, thy micturations are to me, as plurdled globberblotchits on a lurdid bee. Groop I implore thee, my flurling turlingdromes. And hopelessly drangle me with crinkly bindlewurdles, or I will render thee in the globberwarts with my blurdlecruncheon, see if I don't!
(Which can be roughly translated as: Oh beautiful lady, thy beauty is to me, as shining spots on a humming bee. Girl I implore thee, my raging hormones. And hopelessly entangle me with your beauty, or I will render thee in the vagina with my penis, see if I don't!)
Jeltz then asks Ford and Arthur what they think of his poem, and he doesn't care if Ford is human or a Betelgeusian. Arthur reveals he liked the poem, which stuns Ford because he doesn't know about sarcasm. But neither does Jeltz and he decides to throw them off the ship into space for saying that he is nostalgic and lonely. Ford and Arthur are thrown off the ship but are rescued by Zaphod Beeblebrox's spaceship.
The Restaurant at the End of the Universe
Prostetnic Vogon Jeltz is tracking the survivors, Arthur and Ford, furious at having lost them, and Gag Halfrunt is revealed to be the man who ordered Jeltz to blow up Earth and the overall antagonist. Jeltz, however, doesn't like Halfrunt, and Jeltz says he killed half his own crew in a training exercise that morning. Halfrunt simply says this is normal Vogon behaviour and they are happily suited for their jobs.
Jeltz orders his surviving crew to attack Zaphod's ship, but is shocked when the ship doesn't fight back. He pounds the ship with lasers, bullets and tractor beams, but nothing happens. This is because Arthur has told the ship's computers about tea, and thoroughly confused them, resulting in them shutting down. Zaphod decides to hold a seance to talk to his grandfather, while this is successful, his grandfather's ghost slows down time to save everyone. But mainly because he can't stand Zaphod being in the Afterlife with him.
While Jeltz doesn't appear very much in this book, he does influence events, he hires Zarniwoop, an executive, to infiltrate Zaphod's crew and find the ruler of the Universe, which happens, but Zarniwoop is temporarily stuck on the ruler's planet, but he soon escapes and gets revenge by taking over the Guide with Jeltz.
By this time, Prostetnic Vogon Jeltz is back, and he has taken over The Hitchhiker's Guide to the Galaxy offices, and turned them into the Guide Mark Two, an evil device which can find anyone's IP in any universe ever. It is an artificial intelligence and is in league with Jeltz. Ford Prefect steals the Guide, then gives it to Arthur, whose daughter steals it, who takes it to Earth. On this Earth, in another universe, the Vogons are in league with the Grebulon Leader, having found this universe by using the new Guide's IP tracking devices. The Vogons come from Arthur's universe into this one and blow up Earth, and Prostetnic Vogon Jeltz orders the second destruction of Earth. At the end of the demolition, he plays God, ordering "Light" when there is a light switch right next to him. Nothing happens when he says "Light" because the Guide collapses. But Jeltz turns on the light switch himself, and ticks off his assignment. He then flies off into space, mission accomplished.
And Another Thing
As Arthur, Tricia, their daughter Random and Ford were revealed to have actually survived the destruction of the alternate planet Earth, and been transported to Zaphod's spaceship, the Vogons are still in hot pursuit, led by Jeltz, who is absolutely determined to kill Arthur and erase all surviving knowledge of the Ultimate Question. However, he has not counted on his own son, Constant Mown, an enigma among Vogons, who displays compassion for mankind and all that comes with it. Jeltz is about to finally kill Arthur at the climax, but he is thwarted by Constant Mown who has grown to like humans and doesn't wish any more further genocide on his father's hands.