Brother of Zeus and Poseidon, Hades drew the short straw in the competition between the three brothers and was given the onerous task of supervising and ruling over the Underworld as well as all of the precious metal in the world. It is somewhat ironic that Hades should be given power over that which is both radiant and valuable, for it stood in direct contrast to both his personality and his domain. The underworld, a dark and gloomy place, was a place that even the Immortal Heroes were reluctant to enter, for Hades temper and sullenness were legendary across the whole of Greece.
Surrounded by the spirits of those who had died and trapped for eternity in a purgatory state from which there was no escape, Hades found himself increasingly embittered and lonely and as a result hatched a plan to have some company. Persephone, the daughter of the Greek goddess of Fertility, Demeter was kidnapped by Hades and when taken to the Underworld she refused to eat, drink or even speak to Hades. Eventually, Hades tricked the wretched girl by claiming that if she ate just a little of something, then he would return her back to the land of the living. After all he claimed, the last thing he wanted was for the girl to join him permanently as a dead person!
As the myth goes, Persephone swallowed six pomegranate seeds and in so doing so she had in effect accepted Hades hospitality. He attempted to use this as grounds for keeping her down in the Underworld with him forever, and to make her his Queen. Demeter appealed to Zeus on her daughter's behalf to intervene and Zeus decided in his wisdom that Persephone would spend 6 months with her mother, and 6 months with Hades. This story is used to explain why there are different seasons.
His slyness was also further demonstrated when he laid a feast out for Theseus and Pirithous only to ensnare them both.
At other times however, Hades was a rather agreeable fellow and was more than happy to assist Heracles when he entered the Underworld for his final labour, i.e. to obtain Cerberus. Hades made only demand of Heracles: that his beloved pet remain unmolested and unharmed. If Heracles could manage that, then he could do as he wished. Heracles was able to pass through the boundaries of this cold and forbidden land with no problems as a result.