Out of his deep-seated anger against his father Saturn started doing penance (see Birth of Planets). His objective was to become more powerful than Sun, his father.
In Indian Puranas, it was believed that by doing penance, one could gain such powers that one could even topple the seat of Indra (Indian equivalent of Zeus).
During penance, one had to remain celibate, control all his emotions and subject the body to extreme suffering. In summer, one had to stand on one leg within a Ring of Fire or in winter stand neck deep in cold water through the night. All the while chanting specific mantras, which could energize one's latent powers.
Saturn went through this for years and finally achieved success. While Sun gave life to all beings, Saturn became the dealer of Death. He had the additional power of bestowing instant wealth and prosperity and also the power of healing (by denying death).
Even after achieving his goal, he continued to be a celibate and led the life of a hermit. Chhaya, his mother was alarmed. She literally forced him to marry a girl of her choice believing that the beauty of the bride would ensnare Saturn into domesticity.
No such thing happened. Saturn continued with his daily meditation after going through the marriage rituals with extreme reluctance only to please his mother. He remained a celibate, although technically married. It is not clear why he agreed to marry. While agreeing to his mother's entreaties he remained totally oblivious to the fact that in the process he was ruining the life of normal and healthy girl. Possibly he did not quite understand the responsibilities of marriage! His wife tried her best to win him over. She would bedeck herself with all kinds of finery and try to attract his attention. But Saturn did not even looked at her.
One day she had enough of it and cursed Saturn saying "Since you did not even bother to look at me, I curse you that from today whomsoever you look at will perish."
All this while, elsewhere other important things were happening. Mother Uma the consort of Shiva created a child from her mind. The baby was most gorgeous looking and Shiva made him the leader of his guards known as the 'Ganas'. Hence his name became Ganapati or Ganesh.
There is an Indian ceremony when a child receives his first meal of solid food. Family and friends are invited and there are festivities. It is known as Annaprashan.
The time came for Ganesh's Annaprashan. Uma in a joyful mood invited all the gods and demigods. Everybody was too happy to oblige. Everybody except Saturn. Remembering his wife's curse he did not turn up. Uma noticed his absence and sent her emissaries to fetch him. It was difficult to avoid her summons and reluctantly Saturn went. He decided that he would not look at the child and only join the festivities and bless him with his eyes closed.
Alas, that was not to be. Uma brought the child to him and wanted to know what he thought of him. Saturn told her that he did not want to see the child because if he did something terrible might happen.
Uma would hear none of it. She asked Saturn to look at the child and assured him that she herself would remain responsible for the consequences. What could Saturn have done? He looked at Ganesh and as he did Ganesh's head dropped off his shoulder.
Uma was hysterical. There was general confusion. Everybody started crying. Only Vishnu kept everybody cool. He took one of Shiva's attendants aside and asked him go out and find the first living being lying with its head towards the north. He was to cut the head off and bring it as fast as possible to Vishnu.
The attendant found an elephant lying down with its head northwards. He chopped the head off and brought it to Vishnu and he set it on a Ganesh's headless body and Ganesh became whole again. Since then he became known as the Elephant God.
Such were the powers of Saturn - made even more potent by his wife's curse.
In Indian astrology it is said that the house which receives Saturn's aspect (i.e., the house to which Saturn looks) is ruined and nothing good can be expected from it.