Rahu and Ketu
The Head and Tail of the Dragon
Rahu and Ketu arise from Indian mythology and are important in Vedic astrology.
Rahu is the "Dragon's Head" and is associated with the North Node of the moon. Ketu is the "Dragon's Tail" and is associated with the South Node of the moon. Rahu rides a chariot of darkness drawn by eight black horses and is said to be responsible for lunar and solar eclipses.
Rahu was the eldest of 100 brothers, born to Simhika and Viprachitthi. One day Rahu saw Lord Vishnu distributing amrit (ambrosia) to the Gods and Angels whilst denying it to Demons such as himself. Rahu decided to impersonate a God and succeeded in receiving the amrit which made him immortal.
His pretence was discovered by Surya (the Sun) and Chandra (the Moon), who immediately beheaded Rahu. However he had already eaten the amrit and was by then immortal.
His head continued to be known as Rahu whilst his torso became Ketu.
Rahu and Ketu hold an eternal grudge against Surya and Chandra and Rahu takes every opportunity to devour them. This causes an eclipse, which ends when the Sun or Moon emerges from Rahu's severed neck.