Lord vishnu incarnates on Earth from time to
time to irradicate Evil forces and to the store
dharma
Vamanatha god is the fifth incarnation of Lord
Vishnu.
The Bhagwat Purana describes that Lord
Vishnu descended as vamana Avatar to
restore power of Lord Indra over the heavens
which was taken by King Bali.
Indra's Army defeated Devraj Bali and his
Army of asuras.
Unable to accept his defeat devraj bali
approached Rishi Shukracharya to regain his
powers. Shukracharya adviced bali to perform
various yagnas to attain his powers back.
Bali readily agreed and performed various
yagnas under the supetvision of rishi
shukracharya.
Lord indra was scared of bali as he was
gaining all his powers through the yagnasa.
He approached Lord Vishnu and asked for his
help. Lord Indra says to lord vishnu "oh
mighty Lord please save us from bali he have
gained all his powers back by performing
various yagnas.
Lord Vishnu says dont worry indra everything
will fall in place soon
After few days Dev Mata Aditi gave birth to a
baby boy, She named him vamana.
Everyone in the heaven knew that it was lord
vishnu.
Days passed by and vamana hear about Bali
giving arms to the brahmins.
Now lord vishnu in the form of brahman
wanted to check bali's devotion.
One day vamana possed as a Brahmin and
went to the spot where Shukracharya and
Devraj Bali were performing yaga bali
welcomed the Brahmin boy and asked "how
can I help you young brahman"
Vamana says " I have heard a lot about you
giving arms to Brahmins I don't want wealth
or luxuries I just need the land that my three
steps cover all the people sending there were
surprised by the request of The Young
Brahmin the asuras laughed at the boy the
boy did not react on any of them he just
looked at Bali.
Bali says " sure I will give whatever you ask for
go ahead and take three steps of land".
No sooner did bali tell that, the youg boy
started growing in size.
Soon he was larger than the planet earth
itself. He took a large step and put it on earth
to claim it and said "Now the Earth is mine".
He took a large step and put it on heaven and
asked bali " Now the earth and heaven are
mine.Now there is no place left.Where should
i keep my third step?".Bali says " As nothing
else is left you must keep your third step on
my head".Hearing bali's words lord Vishnu
occured in two forms and said "i bless you
bali, From now on you will rule of patal lok
forever". Thus Bali went to patal lok forever.
Indra and other gods reattained heaven due
to lord vishnu's Vamana avatar.