It has been said that in one's astrological chart during the time of birth, If the planets are in between Ragu and Ketu , it is said that the person is born with Kalasarpha dosha facing obstacles in every thing up to 32 years. In Tamilnadu, a temple called Agastheeswarar Temple is situated in Vellore District near Valajah .The Main residing diety is Sri Agatheeswarar and Sri Bhuvaneshwari amman. The diety is said to be a suyambu(born itself) and its under a vanni tree implanted by sage sri agasthiar.
Sri saneeswarar idol below the vanni tree is said to be giving so much relief to persons affected by seven and half years of saturn.
Sri Sarabheswarar is said to be a special diety giving boon soon to all.Ragu kala pooja for sri sarabheswara performed on sundays is very effective.
Visit the link for more information.