In Vaikuntam, Lord Sri Hari has Sri Maha Lakshmi to His service apart from others servants. Sri Maha Lakshmi also has several maids who are charming and beautiful. Shanku Karna is one among the servants of Lord Sri Hari. He was once appointed by Lord Sri Hari to serve Lord Brahma, the Creator.
Lord Brahma took birth from a beautiful lotus that evolved from the navel of Lord Sri Hari. His consort is Goddess Saraswathi Devi. Once Lord Brahma wanted to know where exactly this lotus evolved from. So He followed the stalk of the lotus flower to find it's beginning, only to His vain. He came back and sat in His seat. Yet, His heart was eager to know where the lotus evolved from. Suddenly He heard two alphabets "tha" "pa"(Thapas) from somewhere. He turned around to see who uttered these words and could not find any one. So He decided to do Thapas(Deep Meditation) itself to find an answer. Goddess Saraswathi Devi gave Him a Mantra to recite without any distractions. And Brahma had done it with utmost devotion. Suddenly, the Vaikuntam(abode of Lord Sri Hari) with the Lord Himself, along with His consort Sri Maha Lakshmi appeared in front of His eyes. Ah ! Ultimately He found His birth place(Vaikuntam) ! And He was satisfied. Lord Sri Hari spoke to Brahma and educated Him about the creation and the nature of this Universe. He gave Brahma the Gayatri Mantra and appointed Sri Shanku Karna as Brahma's servant.
Though Shanku Karna was serving Lord Brahma, his heart was totally pre-occupied by Lord Vishnu(Sri Hari). What ever his job was, his heart revolved around the feet of Lord Vishnu. The petals of the lotus seemed like the beautiful eyes of Sri Maha Vishnu to him, the lotuses as the countenence of Sri Hari, their stalks as the beautiful hands, and every part of the lotus seemed to be a part of Lord Sri Hari to Shanku Karna. The swans moving there seemed like Sri Maha Lakshmi Herself. To Shanku Karna's eyes, Sri Vani and Lord Brahma seemed like Sri Lakshmi Narayana.
Once it happened that one day, Shanku Karna was enthralled by the Veena recital of Sri Vani while his heart was meditating about Lord Sri Hari. Lord Brahma noticed this and thought that Shanku Karna was not paying proper attention to His needs. He was angry with Shanku Karna's behavior and cursed him to take birth on earth as a human being. At that time, it was Krutha Yuga in the Bhuloka(Earth). The demon king Hiranya Kashyapa was performing a great penance in favor of Lord Brahma. His wife Leelavathi was pregnant and Shanku Karna entered her womb.
In fact, Lord Brahma was not angry with Shanku Karna but was very happy with the devotion Shanku Karna showed towards Lord Vishnu. The Mother Earth was mourning with the sins that were increasing drastically. To reduce these sins, one such true devotee of Sri Hari was required on the Earth. That was the reason why Lord Brahma had to curse and send Shanku Karna to the Earth.
Whatever might be the reason, Shanku Karna had to leave Vaikuntam and come down to the Earth for a good cause.
Sri Raghavendraya Namaha !!!