The roots of Varaha Avatar start with the doorkeepers of Lord Vishnu. The abode of Lord Vishnu is Vaikuntha Loka. It was guarded by two gatekeepers, Jaya and Vijaya. They loved Lord Vishnu very much and felt honored that they were protecting him.
It was Jaya and Vijaya who would allow people into the Vaikunta Loka to see the Lord. They knew that Lord Vishnu's time was very precious and could not be wasted.
Once it so happened that Lord Brahma's four sons came to see Lord Vishnu in his Vaikunta Loka. However, Lord Vishnu was resting at that time. Thus, Jaya and Vijaya stopped them from meeting Lord Vishnu.
Lord Brahma's sons were very angry with Jaya and Vijaya. They cursed Jaya and Vijaya that they would be born as humans on Earth. Jaya and Vijaya pleaded pardon, but Lord Brahma's sons didn't listen.
After hearing the hustle and bustle, Lord Vishnu arrived at the spot. He apologized for his guards. He said that they were just doing their duty. Lord Brahma's sons told that now they cannot take back the curse and left the place.
Now, Lord Vishnu told Jaya and Vijaya that this curse could only be lifted when they both meet their death at his hands. The guards agreed to this.
In due course of time, Jaya and Vijaya were born as brothers named Hiranyakashyap and Hiranyaksha.
Hiranyaksha was immensely devoted to Lord Brahma. He worshipped Lord Brahma for many years and got the boon that no God, human, Asura, Devta, animal, or beast would be able to kill him.
So, Hiranyaksha became assured of his immortality. He started torturing people on Earth. He was such a giant that the Earth trembled when he walked, and the skies would crack when he shouted.
Hiranyaksha harassed the Devas and attacked Indra's palace in heaven. All the Devas ran for their lives and hid in the caves of mountain ranges of Earth.
Hiranyaksha grabbed the Earth and submerged it in the Patal Loka. So, the Earth sank to the bottom of the ocean.
At this time, Manu and his wife Shatrupa were ruling the Earth. Seeing this, Manu and Shatrupa came to Lord Brahma and told their grief.
So, Lord Brahma told them that they would have to take the help of Lord Vishnu.
Now, Lord Brahma meditated to Lord Vishnu. A tiny boar fell from his nostrils. The creature grew and grew in size until it became the size of a mountain. It was Lord Vishnu. He said that he would enter into the ocean and save the mother earth.
So, Lord Vishnu took the Varaha Avatar (the form of a boar) for killing Hiranyaksha. With a mighty leap, Lord Vishnu dived to the bed of the ocean in search of mother earth. He reached the end of the ocean and discovered Bhumi Devi in its depths.
Meanwhile, Hiranyaksha rushed to the seashore. He encountered Varuna, Lord of the Oceans. He challenged Varuna Deva to have a battle with him. However, Varuna cleverly told Hiranyaksha that he must fight with Lord Vishnu as he is only an equal opponent for him.
At this moment, Narad arrived. Hiranyaksha asked the whereabouts of Lord Vishnu. Narad told him that Lord Vishnu was in the ocean to rescue Mother Earth.
So, angry Hiranyaksha charged towards the ocean bed.
Lord Varaha had dug his tusk into the ocean bed and lifted Mother Earth onto it. He began to move towards the surface.
Hiranyaksha saw Lord Varaha and rushed towards him with his mace. He challenged Lord Vishnu as Varaha Avatar to have battled with him. However, Lord Varaha put the mother earth at a safe place.
Now, Lord Varaha turned to face Hiranyaksha
The demon threw his mace at the Lord. However, Lord Varaha stepped aside. They fought for a long time.
At this time, Lord Brahma warned that he must destroy the demon before sunset so that he gets no opportunity to use his black magic.
So, Varaha Avatar hit Hiranyaksha hard on his face with his fist. He tossed him in the air. Hiranyaksha fell over his head and died on the spot.
Now, Manu got back his Earth, and the Devas got back their heaven. In this way, Lord Vishnu as Varaha Avatar slew Hiranyaksha and saved Mother Earth.