Rahu is considered a greater malefic than Ketu and thus is seen as the most malefic influence in a chart. There is a sort of fear psychosis attached to the interpretation of the nodes especially among the orthodox Vedic astrologers.
One of the reasons for this is that nodes were seen to represent influences, which were not considered proper in the Middle Age’s society and culture. For example they are supposed to bring foreign influences into one’s life, which was seen as a sort of corruption of one’s soul, as all foreigners were looked down upon as outcastes. This was in all probability done to maintain racial genetic purity. Nowadays, since things like foreign travel and foreign influences have become an accepted norm in urban India at least, the more progressive Vedic astrologers are beginning to see the nodes in a different light.
One important rule in Vedic astrology is that a natural malefic can function as a temporary benefic in a chart depending upon its placement and house ownership. Rahu should, like Saturn be seen to work in a benefic way in some cases. He is supposed to pervert or distort the energy of the planet he is associated with by aspect or conjunction. The major period and transits of Rahu are all seen to be troublesome in one way or the other.
Ketu is seen as a natural malefic with a nature similar to that of Mars. He is thus considered a lesser malefic and is seen as a more spiritual planet than Rahu, but he is often considered a bigger hurdle as far as material success is concerned. Rahu is supposed to give material success in some cases but often without inner contentment. Together they are seen to be the cause behind most of the psychological disorders, attraction towards the lower dark side of life, incurable diseases, and possession by negative entities, sudden negative events etc.
The original understanding about Rahu and Ketu as expounded by the ancient seers like Parashara and Jaimini is quite vast and also different in the sense that the positive sides to the nodes are also included. According to them, Rahu represents knowledge and Ketu liberation thus making the nodes the most influential forces in human life. In their works the nodes are not always the villains they are made out to be and can give good or bad results depending upon their placement.
Since the Vedic system does not usually incorporate the outer planets in its analysis, most of the influences pertaining to Uranus, Neptune and Pluto are assigned to the nodes. Rahu is seen as a sort of Uranus and Neptune combined. It is supposed to carry the illusionary, imaginative, hallucinogenic, dissolving, and disintegrating influence of Neptune as it is the planet representing Maya (illusory quality of nature). It is also seen as an eccentric, creative, disruptive, individualizing and revolutionary force that Uranus embodies in the Western system.
Ketu is regarded as a psychic, willful, detaching, penetrating, manipulative, and catastrophic force much in the same way as Pluto is seen in the Western system.
Besides assigning them co-rulership of signs, the Vedic system of astrology or Jyotish assigns rulership of Nakshatras to the nodes. The use of the 27 celestial asterisms spanning the same 360˚ as the constellations is a specialty of Jyotish, as they are not used in Western astrology. This assigning is very important. Besides giving the nodes a cosmological perspective, it is helpful in determining their rulership, exaltation and
debilitation, and deciphering their exoteric and numerological significance.
See for yourself what Rahu and Ketu hare to say in your chart.