In badrinath Dham there are two peaks behind the temple named as Nar & Narayan. In a previous incarnation the duo were supposedly born as the sages
and Narayana,and who performed great penances at the holy spot of Badrinath. Nara and Narayana were the avtar of Lord Vishnu. The twins were sons of Dharma and his wife Murti (Daughter OfDaksha) or Ahimsa..These two sages take avatars on earth for the welfare of mankind .There was an demon named Sahasra Kavacha. He had got boon of having 1000 Kavachas(armours).He had a boon that it will take 1000 Years to break each Kavacha, and the one ,who would break a Kavacha, would instantly die.Hence, first Narayana pennaced for 1000 Yrs and Nara fought 1000 Years with ShahasrKavacha and after 1000 Years, Nara was able to break his one Kavacha. As Nara broke the Kavacha,he died. But Narayan due his penance of 1000 Yrs could get back life of Nara and Narayan starts fighting and Nara starts penance for the next 1000 years.Nara and Narayana alternatively penace and fight for 1000 years and the cycle continued. At last, when they both were able to break 999 Kavachas. ShahasraKavacha hides himself behind the Surya with his last Kavacha due to fear that he would be killed by Nara and Narayana then. At this time, there was Pralaya(destruction) on earth due to the change of the Yuga. Thus ShashtraKavacha escapes death. In Dwapar Yuga,he was reborn as Karna with Kavacha and Nar and Narayan as Arjun and Nara Krishna respectively.