Because of that head of ego, Brahma challenged Bhagwan Vishnu stating that he is superior than him and Bhagwan Shiva. This led to a competition between Brahma and Vishnu, both of them had entered the body of Shiva who had taken the form of a pillar. The condition of victory was that the one who finds either the start or the end of the pillar would win. Vishnu after searching the end point, came out and accepted that the infinite cannot have an end. However, Brahma in order to win the competition lied that he had found out the starting point of the pillar. Shiva then cursed Brahma for lying, saying that Brahma would not be worshipped as the primary deity despite becoming the creator of the material world. But because of the fifth head which represented the ego & ignorance, the words of Brahma’s head came out of arrogance and he insulted Shiva. Blinded by the ego, Brahma forgot that Shiva is unborn and Brahma himself had emerged from Vishnu’s navel, despite being a manifestation of Vishnu.. because of maya (illusion), Brahma declares himself superior to Vishnu and Shiva.
In order to destroy the negativity within Brahma, from the wrath of Shiva appeared a terrifying fierce form of Shiva which was called Kaal Bhairava.
Kaal Bhairava chopped off the 5th head of Brahma just by the nail of the small finger of his left arm. This was to enlighten Brahma, helping him to identify his real self. Brahma is the first and foremost Brahmin who gave all the knowledge. This act of Bhairava cutting the fifth head of Brahma was identified as Brahma hatya, it’s a sin though it was a divine act. Although Bhairava (Shiva) is Almighty, he doesn't need to do any penance for anything, but to give a message that the laws of nature are to be followed, Bhairava roams with Brahma’s skull around the world, that skull gets attached to his hand. He roams and asks the question to everyone but no one could answer, finally he goes to Vaikuntha. Vishnu being the purest, quickly identifies that it was only the leela of Shiva and he asks Bhairava to visit Kashi, the city created by Shiva himself which liberation to everyone. Finally after reaching Kashi, the skull of Brahma gets detached from Bhairava’s hand and falls in a place called Kapal mochan.
So here the message is that it's our ego which makes us blind. Bhairava removes that and makes us aware about the reality. Brahma lied because of ego and got his head chopped off, we as Jeevas are the reflection of Brahma, having both positive as well negative traits. Bhairava removes that negativity within us. Brahma’s skull represents the entire Universe because Brahma is the creator of the Universe, but even higher than the Universe is the destroyer Bhairava who is holding the Universe, Vishnu the operator understands it completely.
So when Shiva asks Bhairava (his own form just different for leela purpose) to roam with the skull, going everywhere, it was Vishnu who was able to give the answer that only Kashi can free him from the sin, it is because he was completely free from ego, he is Achyuta, the infallible since ego cannot touch him. Understanding the leela of Shiva, Vishnu gave the right answer which means that when we will be free from our ahankar, that is when we can see the reality as it is.
This was the Hari Har Leela, here Brahma became the medium in order to give us this message through the divine act.
ॐ नमः शिवाय 🙏 ॐ नमो नारायण 🙏