Rahu and Ketu are extraordinarily important in the interpretation of Jyotisha. The natural strengths of the grahas and the luminaries follow this ascending order-Saturn, Mars, Mercury, Jupiter, Venus, Moon, and Sun. Rahu and Ketu have the natural strength to overcome the Sun and the Moon, so they are, by default, the two most prominent planets in the chart.
Rahu rules over dissatisfaction, panic, phobias, obsessive disorder, mass appeal, desire, ambition, cancers, unrestrained growth, greed, innovation, technological growth, electricity, and mass media. It also rules over unseen influences, black magic, witchcraft, students of magic (including astrology), indulgence in sensual pleasures, boredom, unseen obstacles, frustrations, promises made and not kept, deranged thinking and delusion. Planetary army.
Ketu rules over anonymity, sudden unexpected rise in fame, lack of mindfulness, carelessness, very fine discrimination (which can lead to psychic ability), allergies, infections, bugs, difficultly being recognized, spiritual growth, loss or exposure to thieves. infections, difficult to diagnose illnesses, pest of all kinds, accidents, disasters, fall from position, but can also be an indirect indicator of the strange, unusual, or relationship partners. People with depression often have Ketu afflicting personal planets in the chart. This is also a very selfless or directionless planet, causing confusion. Ketu is an outcast planet.
Since Rahu and Ketu were born from the same being they share traits. Rahu is the head of a serpent/asura; Ketu is tail. Both had great power before they partook of the amrita. They are indestructible. Since Rahu is all sense organs and no stomach to hold anything in, it can never be satisfied. Since Ketu is all body and no head, it has no sense of self and is very irrational and vulnerable and will form an attachment with anything that can direct its energy. Rahu is exalted in Taurus, possibly because Taurus accumulates, Ketu in Scorpio, possibly because Scorpio brings forth the unknown.
Ketu also does well in Sagittarius, Rahu in Gemini, according the the Jamini Sutram and both of the shadowy planets are well placed in Mercury’s signs. Rahu and Ketu have birth places in Aquarius and Leo but own no signs; they act through the lord of the sign in which they are placed. So if Rahu is in a sign (such as Sagittarius) look to Jupiter’s place in the chart and that is how Rahu will manifest. It is the same with Ketu. Both Rahu and Ketu are responsible for so-called deviant (or non-majority consensus) behavior. Rahu acts like Saturn (so it causes some dread and slowness in the chart) and Ketu like Mars, so Ketu can engage in brave selfless battle but is seldom aware of any dangers.