Vishvaroopa was the son of a prajaapathi named Thvashta. He had three heads on his neck and hence was named 'Thishiras' (thri=3, shiras=head) too. (See the links 'Thvashta' and 'prajaapathi'.). Vishvaroopa was also the name of one of four calves of the divine cow surabhi. Be careful to distinguish betwen the same names indicating different persons.
He was very rich in penances. Indra killed him fearing danger to his position from him. Due to that Indra became blemished with sin and he later got rid of it. Thvashta was very angry with Indra again, for killing innocent Vishvaroopa. He created a gigantic demon Vrithra and sent thim to kill Indra. Vrithra defeated Indra but Indra managed to kill Vrithra somehow, with Vishnu's help.
"After praying to Naaraayana, Nara, Sarasvathi and Vyaasa, then one should read the Jayam."
DEDICATED TO MY DEAR NIECE VYSHNAVI KRISHNA