Sastha temple located on the banks of Kulathupuzha, a stream of Kallada River is at a distance of 64 km from Kollam and about 10 km south of Thenmala Railway Station on the Thiruvananthapuram-Shencottai road. Believed to be built by the Raja of Pandalam, the temple has a picturesque location surrounded by beautiful hills and forests. The presiding deity is Manikanda, the child form of Lord Ayyappa or Sastha who is believed to be an incarnation of Lord Vishnu. The most important festival Vishnu Mahotsavam is celebrated in April/May with much magnificence. Lord Shiva in the form of Shiva lingam is another deity in the temple.

Regarding the origin of the temple, there is an interesting story. Once an elderly Brahmin while returning from Rameshwaram pilgrimage camped here. His servants were in search of stones to create a makeshift oven for preparing food. Founding a fixed stone nearby, they brought two other stones to make the oven. But the fixed stone keep growing while they tried to adjust the height and the desperate servants hit the stone with the other and blood gushed out from the stone. The scared servants told the matter to the Brahmin and he sprinkled theertha (sacred water) that he brought from Rameshwaram on the bleeding stone. Soon, Lord Ayyappa in the form of child appeared before the Brahmin and his servants. The King of Kottarakkara heard about this and constructed the present temple. Feeding to the fishes in the nearby river is an important 'vazhipadu' in the Temple.