Palani Hill Temple and the Idol :
Lord Murugan is the deity in Palani (Tiru Avinankudi) . The temple at Palani is an ancient one, situated at an elevation of 1500 feet above sea level . The deity of Palani is known as Dandayudhapani Swami , is the son of Lord Siva and son-in-law of Vishnu. He has other names such as Kulandaivelan, Balasubrahmanyan, Shanmukhan, Devasenapati, Swaminathan, Vallimanalan, Devayanaimanalan, Palaniandavar, Kurinjiandavar, Arumugan, Jnana Pandita, Saravanan, Sevar Kodiyonthe. The deity at the sanctum sanctorum is made out of an amalgam of nine minerals popularly called Navabashana. The Lord having the Staff in his Hand. The deity is in a standing position with a baton in his hand. He has the look of a person who has renounced all worldly pomp. He has just a loincloth besides the baton. He is a mute messenger of the great precept 'Renounce all to reach Me'. The icon is unique in the whole world. It was made by siddha Bhogar by combining nine poisonous substances (navabashana).
The Legend or Sthala Purana of Palani :
As per the Hindu mythology, Sage Narada once visited the divine court of Lord Shiva at Mount Kailash. Lord Shiva was with his consort, Goddess Shakti, and their two children, Lord Ganesha and Lord Subrahmanya. Sage Narada gave Lord Shiva a fruit and told him that it was a special one, the fruit of wisdom (Jnana-Pazham).
Lord Shiva wanted his children to have the fruit of wisdom. However, when he offered it to them to be shared between the two sons, Sage Narada requested not to cut the fruit in two, lest the power be diminished. As a result, they had to decide to conduct a simple competition to decide who should get the fruit. Shiva and Shakti decided that the son who first circled the Earth would get the fruit. Immediately accepting the challenge, Lord Murugan started his journey around the globe on his divine vehicle, the peacock. Lord Ganesha, who believed that his parents were his world, simply circumbulated Lord Shiva and Goddess Shakti and claimed the mango fruit. Lord Subrahmanya returned to Mount Kailash, only to find that Lord Ganesha had already won the contest. Lord Murugan felt he had been deceived and decided to leave Mount Kailasam. He reached to top of what is today called Pazhani malai and set up his abode there. Goddess Shakti and Lord Shiva rushed to the hill and tried to pacify their son, calling him, Gnana Pazham Nee appa (in Tamil, "you are the fruit - Pazham; of wisdom - Gnana"). Hence this place came to be called Pazhani, or Palani.
Lord Shiva wanted his children to have the fruit of wisdom. However, when he offered it to them to be shared between the two sons, Sage Narada requested not to cut the fruit in two, lest the power be diminished. As a result, they had to decide to conduct a simple competition to decide who should get the fruit. Shiva and Shakti decided that the son who first circled the Earth would get the fruit. Immediately accepting the challenge, Lord Murugan started his journey around the globe on his divine vehicle, the peacock. Lord Ganesha, who believed that his parents were his world, simply circumbulated Lord Shiva and Goddess Shakti and claimed the mango fruit. Lord Subrahmanya returned to Mount Kailash, only to find that Lord Ganesha had already won the contest. Lord Murugan felt he had been deceived and decided to leave Mount Kailasam. He reached to top of what is today called Pazhani malai and set up his abode there. Goddess Shakti and Lord Shiva rushed to the hill and tried to pacify their son, calling him, Gnana Pazham Nee appa (in Tamil, "you are the fruit - Pazham; of wisdom - Gnana"). Hence this place came to be called Pazhani, or Palani.
Bhogar Shrine :
The Bhogar Shrine is in the southwestern corridor of the hill temple. Siddhar Bhogar created the icon (the amalgam of nine minerals) and did daily services. He lived long ago, perhaps 3000 BC.
Legend also has it that a divine siddhar named Boghar, created the idol of Dhandayuthapaani using navapashanam, an amalgam made from 9 poisonous elements which on getting mixed develops highly curative powers for many ailments of the human body, according to Sidhha Medicine practice. A small portion with a deity, dedicated to Boghar is also placed inside the temple. the adjoining walls depicts the history of the creation and other facts related to the temple. In this shrine, pujas are offered to Navadurga, Bhuvaneswari and Maragatha Lingam that were worshipped by Bhogar. It is said that there is a subterranean tunnel linking the shrine with the sanctum sanctorum through which Bhogar is said to go to the main idol and perform daily pujas as he is said to be only in nirvikalpa samadhi.
How Kavadi Tradition Began :
The Kavadi is steeped in Mythology. At Mount Kailash, Lord Shiva entrusted the saint sage 
Agastya with two hillocks , Sivagiri and Sakthigiri (A small natural hill), with the instruction to carry and install them in South India. But the sage left them in a forest and later asked his disciple, Idumban to get them. Idumban found the two hillocks, but could not intially lift them , untill he obtained divine help. Near Palani in south India, Indumban Kept the hillocks down to rest awhile. When he attempted to continue with his journey , he found that the hillocks were immovable. He then sought the help of a scantily dressed youth , but the youth claimed the hillocks belonged to him. In the ensuing scuffle, Idumban was defeated. Idumban the realised that the youth was Lord Muruga. He pleaded to be pardoned and asked that anyone comes to hills to worship Muruga with an object similar to two hillocks suspended by a rod , may be granted his heart's desire. Idumban's wish was granted, and so the Kavadi came to play its role on the festivals.
Agastya with two hillocks , Sivagiri and Sakthigiri (A small natural hill), with the instruction to carry and install them in South India. But the sage left them in a forest and later asked his disciple, Idumban to get them. Idumban found the two hillocks, but could not intially lift them , untill he obtained divine help. Near Palani in south India, Indumban Kept the hillocks down to rest awhile. When he attempted to continue with his journey , he found that the hillocks were immovable. He then sought the help of a scantily dressed youth , but the youth claimed the hillocks belonged to him. In the ensuing scuffle, Idumban was defeated. Idumban the realised that the youth was Lord Muruga. He pleaded to be pardoned and asked that anyone comes to hills to worship Muruga with an object similar to two hillocks suspended by a rod , may be granted his heart's desire. Idumban's wish was granted, and so the Kavadi came to play its role on the festivals.Pooja :
There are six pujas every day . At 5 am the Lord gives Visvarupa Darshana and finally ends with Golden Charriot Darshan.
- Vilaa Pooja (6.30 a.m.)
- Siru Kall Pooja (8.00 a.m.)
- Kaala Santhi (9.00 a.m.)
- Utchikkala Pooja (12.00 noon)
- Raja Alankaram (5.30 p.m.)
- Iraakkaala Puja (8.00 p.m.)
Festivals :
Panguniuttiram, Thai Pucam, Kanda Sasthi, Agni Nakshatram are the major festivals. Vaikasi Vishakam, Tirukkarttikai and other festivals are also celebrated.
Pictorial representation of the story of how Palani gots its name :
check this link , where the whole story is well explained through photos :
