Why Was Aghasura Promoted To The Vaikuntha Planets? by His Divine Grace A.C.Bhaktivedanta Swami Prabhupada
Apparently the serpent named Aghasura, because of having received association with Kṛishṇa, attained mukti by entering Kṛishṇa’s body. Entering the body of Krishna is called sāyujya-mukti. However, Aghasura, like Dantavakra and others, received sārūpyamukti.
This has been broadly described by Srila Vishvanatha Chakravarti Thakura with references from the Laghu-toṣaṇī of Srila Jiva Goswami. Promoted to the Vaikuntha planets to live with the same four-armed bodily features as Lord Vishnu, Aghasura attained sārūpya-mukti.
This is explained further in the following section. The effulgence came out from the python’s body and it became purified, attaining spiritual śuddhasattva, freedom from material contamination, because Krishna had stayed within the serpent’s body, even after the serpent’s death. One may doubt that how such a demon with horrendous activities could attain the liberation of sārūpya or sāyujya, and one may be astonished about this. But Krishna is so kind that in order to drive away such doubts, He made the effulgence, the individual life of the python wait for some time in its individuality, in the presence of all the demigods.
Kṛishna is the full effulgence, and every living being is part and parcel of that effulgence. As proved here, the effulgence in every living being is individual. For some time, the effulgence remained outside the demon’s body, individually, and did not mix with the whole effulgence, the brahma-jyoti. The Brahman effulgence is not visible to material eyes, but to prove that every living being is individual, Krishna had this individual effulgence stay outside the demon’s body for some time, for everyone to see. Then Krishna proved that anyone killed by Him attains liberation, whether sāyujya, sārūpya, sāmīpya or any other.
However, the liberation of those who are on the transcendental platform of love and affection is vimukti, special liberation. Thus the serpent first entered the body of Krishna personally and mixed with the brahman effulgence. This merging is called sāyujya-mukti. But from later verses we find that Aghasura attained sārūpya-mukti.
naitad vicitraṁ manujārbha-māyinaḥ
parāvarāṇāṁ paramasya vedhasaḥ
agho ‘pi yat-sparśana-dhauta-pātakaḥ
prāpātma-sāmyaṁ tv asatāṁ sudurlabham
Krishna is the cause of all causes. The causes and effects of the material world, both higher and lower, are all created by the Supreme Lord, the original controller. When Krishna appeared as the son of Nanda Maharaja and Yashoda, He did so by His causeless mercy. Consequently, for Him to exhibit His unlimited opulence on other occasions was not at all wonderful. Indeed, He showed such great mercy that even Aghasura, the most sinful miscreant, was elevated to being one of His associates and achieving sārūpyamukti, which is actually impossible for materially
contaminated persons to attain.
This verse explains that Aghasura attained a body exactly like that of Lord Vishnu, and the subsequent verse also clearly states that he attained a completely spiritual body like that of Narayana.
manomayī bhāgavatīṁ dadau gatim
sa eva nityātma-sukhānubhūty-abhivyudasta-
māyo ‘ntar-gato hi kiṁ punaḥ
If, one brings the form of the Supreme Personality of Godhead into one’s mind, only one time, or even by force one can, by the mercy of Krishna, attain the supreme salvation, as did Aghasura. What then is to be said of those whose
hearts the Supreme Personality of Godhead enters when He appears as an incarnation? Or those who always think of the lotus feet of the Lord, who is the source of transcendental bliss for all living entities and by whom all illusion
is completely removed, What mercy will they receive?
Therefore in two or three places the Bhāgavatam has confirmed that Aghasura attained sārūpyamukti. One may then argue, how is it that he mixed with the Brahman effulgence? The answer is that as Jaya and Vijaya, after three births, again attained sārūpya-mukti and association with the Lord, Aghasura received a similar liberation.
— Śrīmad-Bhāgavatam (BhāgavataPurāṇa) » Canto 10: The Summum Bonum » Chapter.12: The Killing of the Demon Aghāsura.