Often when all then seven planets including moon comes in between the axis called Rahu ( Dragons head or North Node) and Ketu ( Dragons Tail or South Node), it is called Kaal Sarp Yoga or even Kaal Sarp Dosha. It is considered to have malefic effects on individual in astrology. Here Kaal is referred as passage of time , Sarp as serpant and Yoga means energy. This simply refers to destiny or prarabdha along with kriya.
There is quite a mystery surrounding this approach in astrology. Some stalwarts of astrology completely deny this Yoga (combination of aspect and placement) while others are ardent believers of its presence and effects. The basic reason to deny is that they there is no clear presence or description of it in ancient texts of astrology. While the secrets of Tantra, Kundlini, Shaivnism and Karmic astrology founds it in the very base or foundation of existence. When any combination talks about time, energy and existence, I think it cannot be denied mere on the basis of no reference in texts. How can we deny that even Rahu and Ketu are not planets but crossing points which have been awarded the class of planets due to their so much importance as energy field. They are so important that they not only have their presence or positional effect but also signify the stars they are into, sign they are placed, planets they co join and even plant they form aspects. In light of above I think we have to see Kal Sarp Dosha from altogether different perspective. Without .