Sahasrakavach

 

karna is a rakshasa called sahasrakavach....get 1000 armours from lord shiva.....in order to destroy one armour one has to do penance for 100 years...so lord vishnu takes form of nar and narayan and performs penance...while nar fights shasrakavach, narayan performed penance for 100 years and when narayan fights nar use to perform penance and vice versa,they destroys 999 armours of the rakshasa,sahasrakvach will run out of fear to sun god,the sun god turns the rakshasa to a baby and give it to kunti who is karna the last Armour must be destroyed by nar,so this nar is re-incarnated as arjuna and narayan as krishna.....that is the reason why krishna cannot kill karna by his sudarshan chakra..it is not true that it cannot be penetrated by sudarshan chakra