The vow of the Asuras was (according to the Burdwan Pundits) never to drink wine. It is more rational to suppose that Karna swears to give up the refined manners and practices of the Arvas and adopt those of the Asuras till the consummation of the cherished desire.
“Meanwhile those mighty bowmen, the Pandavas, excited by the words the messenger had spoken, became anxious, and they did not (from that time) experience the least happiness. Intelligence, further, O foremost of kings, had been brought by spies regarding the vow of the Suta’s son to slay Vijaya. Hearing this, O lord of men, Dharma’s son became exceedingly anxious. And considering Karna of the impenetrable mail to be of wonderful prowess, and remembering all their woes, he knew no peace. And that high-souled one filled with anxiety, made up his mind to abandon the woods about Dwaitavana abounding with ferocious animals.
“Meanwhile the royal son of Dhritarashtra began to rule the earth, along with his heroic brothers as also with Bhishma and Drona and Kripa. And with the assistance of the Suta’s son crowned with martial glory, Duryodhana remained ever intent on the welfare of the rulers of the earth, and he worshipped the foremost of Brahmanas by celebrating sacrifices with profuse gifts. And that hero and subduer of foes, O king, was engaged in doing good to his brothers, concluding for certain in his mind that giving and enjoying are the only use of riches.”
Janamejaya said, “After having delivered Duryodhana, what did the mighty sons of Pandu do in that forest? It behoveth thee to tell me this.”
Vaisampayana said, “Once on a time, as Yudhishthira lay down at night in the Dwaita woods, some deer, with accents choked in tears, presented themselves before him in his dreams. To them standing with joined hands, their bodies trembling all over that foremost of monarchs said, ’Tell me what ye wish to say. Who are ye? And what do ye desire?’ Thus accosted by Kunti’s son—the illustrious Pandava, those deer, the remnant of those that had been slaughtered, replied unto him, saying, ’We are, O Bharata, those deer that are still alive after them that had been slaughtered. We shall be exterminated totally. Therefore, do thou change thy residence. O mighty king, all thy brothers are heroes, conversant with weapons; they have thinned the ranks of the rangers of the forest. We few—the remnants,—O mighty-minded one, remain like seed. By thy favour, O king of kings, let us increase.’ Seeing these deer, which remained like seed after the rest had been destroyed trembling and afflicted with fear, Yudhishthira the just was greatly affected with grief. And the king, intent on the welfare of all creatures, said unto them, ‘So be it. I shall act as ye have said.’ Awaking after such a vision, that excellent king, moved by pity towards