Do you remember Rahu, the demon decapitated by Vishnu during the 'churning of the ocean'? Well, one day he was used by Jalandhara, demon tyrant very complex origins of that one day I will say, as his messenger.
Jalandhara was master of the three worlds and, thanks to his hard austerities, had immense power, but someone pointed out that he didn't have all. He missed Parvati, the most beautiful woman in the world, the goddess who had been married to Lord Shiva.
"Shiva, the ascetic beggar, why did he have a woman so beautiful?" wondered Jalandhara. "I want her!"
That said, he called Rahu and sent him as his ambassador to Shiva.
"Go to Shiva and tell him to give me Parvati, if he refuses, it will be war."
As a good messenger, Rahu went to Shiva and told him the request of his master.
Heard the request, Shiva became furious and was born from his third eye a terrible creature with a lion's mane, eyes of fire, its body thin and emaciated. A monster violent and very strong, but above all very hungry who immediately pounced on Rahu.
The victim turned to Shiva, the asolute god and begged to be spared.
Shiva intervened and ordered the demon not to eat Rahu.
"And then who am I eating? You created me with this insatiable hunger, like I can at least soothe it? "
"Eat yourself," said Shiva.
And so, the monster ate its own legs, its arms, its bodies and he was only one furious head.
"Henceforth - Shiva told him - you'll be Kirtimukha, the glorious face. I want you always in front of my door and who will enter my home without having worshiped before you, he will not get anything of what he asks for. "
For this reason, on the portals of the Hindu temples, palaces, and houses there is often a monstrous face, is the face of glory, Kirtimukha.