Lord Shiva is called Swayambhu. Which means he is unborn. Shiva is neither beginning nor end, Bholenath is called unborn and imperishable. After all, what is the mystery related to the birth of Shiva?
Devadhidev Mahadev Shiva Shankar has got first place in the Puranas. Prajapita Brahma as the creator, Jagatpalak Lord Vishnu as the protector and Lord Shiva as the destroyer. It is said that this trinity, together with the creation, maintenance and destruction of nature, indicates that whatever has been created is bound to be destroyed.
The origin of this trinity is itself a mystery. Many Puranas believe that Brahmaji and Jagatpalak Lord Vishnu originated from Shiva, but the question always arises in the minds of Shiva devotees how did Lord Shiva take birth?
Lord Shiva is said to be swayambhu, which means he is not born out of a human body. Lord Shiva was there when there was nothing and he will exist forever even after everything is destroyed. Lord Shiva is also called Adidev, which means the oldest deity in Hindu mythology and he is the first among the gods.
A story regarding the birth of Lord Shiva is mentioned in the scriptures. Once upon a time, there was a debate between Brahmaji and Lord Vishnu about who is the greatest and best amongst both of us. Then Mahadev himself took the form of a mysterious pillar to test both of them. When the side and end of the pillar were not visible, then Brahmaji and Vishnuji heard an Akashvani, in which they were asked to find the first and last end of the pillar.
After this Brahmaji immediately assumed the form of a bird and set out to search for the upper part of the pillar and Lord Vishnu took the form of Varaha and set out to find the end of the pillar. Both tried a lot but failed. When both of them gave up, Lord Shiva who was in the form of a huge pillar appeared in his original form. Then Brahma ji and Vishnu ji believed that a supreme superpower is running this entire universe and that superpower is the self-styled god Mahadev Shiva. There is such a mythological story that the never-ending form of Lord Shiva in the form of a pillar symbol was later worshiped in the form of Shivling.
Apart from this story, there are many other stories about the birth of Lord Shiva. Eleven incarnations of Shiva are considered and the story of Rudravatar is considered to be prominent in the stories of these incarnations. According to Kurma Purana, when Brahma ji started having difficulty in creating the universe and crying out to Devadhidev Mahadev, then ghosts and demons were born from the tears of Brahma ji and Rudra was born from his mouth. Rudra is the part of Lord Shiva and the ghosts and spirits are considered to be his Gana i.e. servants. Thus the universe was created by the grace of Shiva.
According to Shiva Purana, Lord Shiva is believed to be Swayambhu (self-born), according to Shiva Purana, once when Lord Shiva was rubbing nectar on his ankle, Lord Vishnu is said to have been born from it. Lord Shiva, who is called the destroyer, once drank poison to protect the gods and came to be known as Neelkanth. It is said that if Lord Shiva is pleased with his devotees, then Bhole Baba fulfills all the desires of the mind. Such is Bhole Baba Mahadev.