Markandeshwar Mahadev had appeared with the blessing of Shiva.

The temple of Shri Markandeshwar Mahadev comes at the 36th position in the series of eighty-four Mahadevs. By visiting and worshiping them, man becomes filled with happiness and prosperity and attains the supreme state.

Penance in the Himalayas with the desire to have a son
Years ago there used to be a Brahmin named Mrikand. He was always engrossed in the study of Vedas. Time passed and they started worrying that they did not have a son. With the wish of having a son, he went to the Himalayas and started rigorous penance. Due to his penance, a situation of famine and setting of the sun and moon began to arise in the universe.

Shiva was pleased with the penance of the Brahmin.
On this, Mother Parvati told Lord Shiva that it is your devotee who is doing penance. You fulfill his wish. Shivji said, O Parvati, on your request, I will definitely complete his penance. You ask the Brahmin to worship the son-giving Shivalinga located east of Pattaneshwar in the Mahakal forest. After hearing such a voice from the sky, the Brahmin went to Mahakal forest and started worshiping Shivalinga. Shiva-Parvati appeared from Shivalinga and gave the Brahmin the boon of having a son.

This Shivling will be famous by your name
With the blessing of Shiva, Mahamuni Markandeya appeared there. On this he immediately sat down to worship Shiva. Seeing Markandeya doing penance, Lord Shiva said that the Shivalinga you are worshiping will now be famous all over the world in your name.

By worshiping Markandeya, Shivalinga became famous by the name of Markandeshwar. Whoever worships this Shivalinga with full devotion will always be happy and will attain the supreme state.