Kalakeyas were born to Sage Kashyapa and his wife Kalaka.
Adi Parva of Mahabharata states that there are 60,000 Kalakeyas. They performed
numerous Adharmic activities including disturbing Vedic rituals, murders and
looting.
Once a yajna of Sage Agastya was disturbed by Sage Agastya.
Unable to face the anger of Sage Agastya, Kalakeyas hid in the ocean. The Sage
immediately drank up the water of ocean and annihilated numerous Kalakeyas.
Those Kalakeyas that escaped took refuge in netherworld.
They again started disturbing human beings and saints.
Once they attacked heaven. Indra took the help of Arjuna,
the third of Pandavas. Arjuna then killed the remaining Kalakeyas.
The incident is famous because when Arjun reached heaven,
Urvashi, the damsel, fell in love with Arjuna. But Arjun did not reciprocate
the love. An angry Urvashi cursed Arjuna to become a Eunuch. Later, Indra
changed the curse that Arjuna will only have to live the life of Eunuch for a
year.
Arjuna used this curse when he had to lead the life of Brihannala,
the dancer in the palace of King Virata.. Thus, the curse turned to be a great
help to Arjuna, when he had to hide disguised during the thirteenth year of
exile period in the Mahabharata.