In Hindu mythology Rahu is a demon. In astrology he is one among the Navagraha; though he along with Kethu, do not have a physical body like other grahas. He is the chief advisor to asuras and a master manipulator.
He is depicted as a snake without body.
There is a legend behind this unique depiction. A demon called Rahu tried to drink the nectar (that came out during Palazhimathan or churning of the milky ocean) by taking the form of a deva. But before the nectar could pass his throat, Lord Chandra discovered the demon in disguise. Lord Vishnu, who was supplying (as Mohini) the nectar, cut off the demon’s head with his Sudarsan Chakra. Though the body-part was dead, as Rahu already had some nectar on his neck, it became immortal while the rest of body became Kethu.
Thus a grudge was there with these grahas to Surya and Chandra. They occasionally swallow Sun or thr Moon, causing eclipse.
In Hindu astrology, his displeasure can cause communicable diseases like leprosy, mental disorder, problems to one’s wife or son and sudden fall in grace, etc…
All poisonous substances, especially snake bite and chemicals are also associated with him.
On the positive side, when pleased he helps a person to befriend even an enemy. Success of one’s effort also comes with his grace.
He provides direction to one’s voyage of life. Knowing the position of Rahu in a person’s horoscope helps him in planning his life to success.
His favorite color is smoky. Metal is Lead
Gem stone is honey colored hessonite and the associated element is Air.
The vast temple, even otherwise popular as a Lord Shiva shrine, is seven kilometers from Kumbakonam.