It is about the ancient history of Adi Anadi Sayumbhu Tapkeshwar Mahadev. It is here that Guru Dronacharya did his penance for twelve years, known as Drona Cave or Guffa. Here in Dehradun, it is an ancient piligrimage centre where devotees from all over India, and fare flung areas, come to seek the blessings of Lord Shiva. Before the advent of battle of Mahabharata, Sri Dronacharya went on a pilgrimage. He visited several places in the Himalaya mountains. During hid pious travels, he met a Rishi-Raj and postrated at his feet. Rishi-Raj knew the purpose of his wonderings and told him, that very soon your desires will he fulfilled with tears in his eyes, he asked the Rishi-Raj when and where Lord Shiva would appear before him and bless him. Rishi asked him to travel towards Rishi-kesh. On the way you will find river Ganges and river Yamuna and another river flowing near by, which is called Tamsa river. On the banks of this river, there is a super natural celestial cave. In this cave you will find self existent (Sayambhu) Shiv-ling. Devtas also use to come and do penance in this cave and Lord Siva in the form of Deveshwar Mahadev, would appear before them and bless them and their desires use to get fulfilled. So I advise you, to go and do pious penance in that celestial cave. Nowadays this heavenly cave is famous by the name of Tapkeshwar Mahadev. Lord Shiva is very generous towards his pious devote and He fulfills their, all ambitions and desires. Sri Dronacharya travelled and found the celestial cave. Both he and hi s wife Kripi were spell bound seeing the Siva-ling. This cave was situated on the bank of Tamsa river, which was flowing in a magestic form, gurgling all the way. To his astonishment he saw lion and deer drinking water at the same spot, without any enimity towards each other. There were many more caves nearby, where he found Rishis and Munnis doing hard penance. He got water from the Tamsa river and white flowers which were growing nearby. With these in his hands, he and his wife Kripi entered the cave. They postrated in front of the Shiva-ling and offered water and flowers. Both Sri Dronacharya and Devi Kripi got so engrossed and absorbed in their Tapasaya and in this way, twelve years passed by. Lord Shiva was so happy with their pure devotion, that He appeared in front of them. He said “I am extremely happy with your penance and I will fulfill all your wishes and desires". With folded hands Sri Dronacharya got up and asked Lord Shiva to teach him the art of Archery, for the up liftment of mankind and universal peace. Daily Lord Shiva would manifest Himself and give him the lessons on Archery. Sri Dronacharya became very competent in Archery and he also became expert in the use of weaponary knowledge.
Devi Kripi used to be alone and sad and one day her husband asked her the cause of her unhappiness. She related, that all those years she had been travelling with him through jungles, hills and dales, but now she had a desire to have a child of her own, to give her solace Sri Dronacharya asked her to worship Lord Shiva, with utmost devotion. Sri Dronacharya told Kripi that Lord Shiva was very kind hearted, omnipotent, omni present and he would get her dreams fulfilled. Both husband and wife would worship Lord Shiva and one day He appeared before them and blessed them with a progeny. After some months Devi Kripi gave birth to a healthy, strong and handsome boy. The boy would cry like a horse “Ashav". Devtas also blessed the boy. Because of his peculiar crying, the boy was named Ashwathama.