Rahu and Ketu
Rahu and Ketu are two mysterious forces in the birth chart that show both karmic and spiritual influences. Astronomically speaking either node can bring about an eclipse of the Sun or Moon but symbolically Rahu is associated with the eclipse of the Moon and Ketu is concerned with the eclipse of the Sun.
A lunar eclipse defines the nature of Rahu when a shadow forms over the Moon. This shadow is the darkness of the sub-conscious mind and the Tamasic forces of the lower chakras that bind us to negative behavior patterns like addictions and other neurotic habits. The Moon represents the feeling nature, sensitivity and receptivity of a person so the association of the Moon with Rahu can show a mind under malefic astral influence. This can produce an intelligent but cunning nature and in the worst scenario a charismatic sociopath.

The chart above is of Jim Jones is as example of the association of the Moon and Rahu. Firstly the karaka of a house should not occupy that house and here we have the 8th lord Moon in the 4th house within 1 degree of Rahu. This house also has the aspect of Saturn further darkening it. The natural 4th house of Cancer is also afflicted by Rahu, Saturn and Mars. Mars the ava yogi planet also falls on the Mrityu Bhaga degree of 23 in the 8th house of death showing a quick and violent death. The 4th lord Jupiter and dispositor of both Moon and Rahu is blemished by kendra adypathya dosha being the ruler of two kendras in a kendra from the Moon. This of course is an extreme example but shows this influence of Rahu in the chart of a man who had many people under his spell but was in hindsight a dangerous lunatic. Rahu in particular can show the negative influence and illusion of mass trends and cults.

Another example is the horoscope of Iraqi leader Saddam Hussein who has the close association of the Moon and Mars in the same sign as Rahu in Scorpio. While the aspect is not so close between the Moon and Rahu it would be fair to say anger and violence afflict Saddam's mind, as Mars is retrograde in it's own home afflicting the Moon and 4th lord Mercury. In fact the nodes and Mars afflict both planets of the mind. Mars is in the 6th house of enemies, no wonder he has destroyed anybody who even looks like a threat to his power. The exalted Sun shows a man who yields to no one. His lagna lord Mercury has the blemish of kendra adypathya dosha also, as well as the afflictions of Rahu, Mars and Saturn. Rahu has a deeper influence on him as the lagna falls in the nakshatra of Ardra a sharp and dreadful nakshatra ruled by Rahu whose deity is the storm god Rudra. His natal Rahu sits in the nakshatra of Jyestha ruled by the lagna lord Mercury. At present his 8th lord of death is in transit over his lagna lord Mercury in the 12th house of endings. He is running Moon/ Venus period and Venus is lord of the 22nd drekkana and Mercury the lagna lord is located in it. Venus is in the nakshatra of Mercury the lagna lord so I will not be surprised if he dies soon.
Rahu and Ketu are symbolic of the duality of mans nature with Rahu representing the base of the spine and the lower chakras and Ketu representing the top of the head and the higher chakras of the third eye and crown chakra. This is symbolized in all religions as the battle between the forces of darkness and light. In every field of religious thought there is this concept of ascending out of the darkness into the light to find God. The real meaning of the word Guru is actually "remover of the darkness." A "Guru" indicates a person who can help us ascend from the dark depths of our own sub-conscious mind and lower nature to higher realms of consciousness where selflessness, compassion, wisdom and kindness help us see through the illusion that any form of matter can be permanent.
Every form of physical existence is in a state of either creation, preservation or destruction and the contracting nature of Ketu can reveal this to us. During an eclipse of the Sun we can sense that nothing is permanent, even the rays of the Sun that are always present vanish and we are left in the darkness. The stars that are not usually visible during the day become visible during a solar eclipse. This shows Ketu can not only negate the things it associates with but can also reveal things that may otherwise stay hidden.

The above chart is of the Dalai Lama, one of the world's great spiritual leaders who selflessly works in promoting the Dharma of the Buddha. He was born in the 4th sign of the zodiac in the sign of the Mind and the Moon is in association with the 4th lord Venus a kind and sweet planet. His Sun as dispositor of the lagna lord Moon is in the 12th house of Moksha associated with Ketu and Mercury. Ketu is more or less in rapt conjunction with the lagna cusp by degree. Mercury as the 3rd lord of mental outlook and natural karaka of speech and communications is also the 12th lord in the 12th house with Ketu. This is said to show mastery of that house and in the Dalai Lamas case it shows divine speech and a person who has the spiritual authority to speak about enlightenment and afterlife issues. The Moon and Venus together also show a kind face and a pleasant voice. Jupiter is in the 4th house of the mind and emotions in the nakshatra of Vishaka. Lord Buddha is said to have been born on a full Moon day with the Moon placed here also. The Sun and Ketu are both placed in the nakshatra of Jupiter and this indicates the negation of the self and the divine nature of his mind. The Sun and Jupiter are in exact trine putting them both in the 10th house in the navamsha where the Sun is exalted.
One important point in interpreting the effects of the nodes is we must look at their dispositors and where they are situated in relationship to each other. The dispositors of the Dalai Lamas nodes are Jupiter and Mercury. Two benefics who are in trine to each other and very well placed for a spiritual leader. His Rahu is also in the 9th sign of the zodiac in the 6th house of service. The dispositor is Jupiter the 9th lord of the divine, so the aspect of Rahu on the Moon here can only be benefic. Venus is the 4th lord of the homeland and is ava yogi planet with the aspect of Saturn. Venus falls in the nakshatra of Magha, ruled by Ketu who is in the 12th house of loss. The problems in his homeland would have caused him great suffering as Venus is with his lagna lord and natural karaka of the emotions Moon. Their close association shows his love of his homeland but the aspect of Saturn the 8th lord from the 8th house show death like sorrow concerning this.
The point about the dispositors is at best, they can only be neutral to each other. This is similar to the problem with relationships between people where the lord of the lagna and the 7th lord are often enemies. If these planets are then placed in bad aspect to each other the person is unbalanced to start with in terms of being able to have a harmonious relationship. This is also very important when trying to judge the effects of the nodes. In great spiritual leaders charts there is usually a good temporal relationship between the dispositors of the nodes.

Another example is the chart of Ramakrishna one of India's greatest saints. He was born in Aquarius lagna and the dispositor of Ketu is Mars exalted in the 12th house of Moksha. Rahu is in the 4th house of the mind and emotions and its dispositor is Venus exalted in the 2nd house. Both dispositors are in 3/11 aspect, a harmonious aspect and both are exalted. Mars is in the 12th house and Venus in the 12th sign. Jupiter is in the 5th house in good aspect to Sun, Moon and Mercury. Saturn is in the 9th house exalted also, so there is a wonderful grand trine between the Sun, Moon, Jupiter and Saturn.
In a weak horoscope the effect of Rahu must be carefully checked as it can show where a person has the greatest illusions about life. In the chart of Michael Hutchence we can see the dispositors of the nodes are well placed from each other but the 12th house and Venus in particular are badly afflicted. This shows why he was using drugs and sex as his experience into moksha states. The ecstasy felt during comfortable sleep or while enjoying sex or the intoxicating effects of drugs is a mini state of moksha and if the 12th house is afflicted it can show a person who experiments with sex, drugs and other activities practiced in private. They are actually after that euphoric state experienced when there is no sense of self.
This was the basis of my original comment about the man going to the Church and the man going to the Brothel. Both are after some form of fullfilment. I said the man visiting the brothel is more likely to find what he is looking for. This was not some crude remark but a reference to the difficulty in overcoming the self and the cravings of human desire.
Either node, but particularly Rahu when well placed and well aspected can become the greatest benefic and give excellent results. Either Node can be either very malefic, benefic or give mixed results. Simplistic interpretations cannot be given in relationship to the nodes. They must be understood in terms of a holistic assessment of a horoscope.
A part is never the whole.