When Svāyambhuva Manu saw that Dhruva Mahārāja understood the philosophy of Vaiṣṇavism and yet was still dissatisfied because of his brother's death, he gave him an explanation of how this material body is created by the five elements of material nature. In the Bhagavad-gītā it is also confirmed, prakṛteḥ kriyamāṇāni: (BG 3.27) everything is created, maintained and annihilated by the material modes of nature. In the background, of course, there is the direction of the Supreme Personality of Godhead. This is also confirmed in the Bhagavad-gītā (mayādhyakṣeṇa (BG 9.10)). In the Ninth Chapter, Kṛṣṇa says, "Under My superintendence material nature is acting." Svāyambhuva Manu wanted to impress on Dhruva Mahārāja that the death of the material body of his brother was not actually the Yakṣas' fault; it was an act of the material nature. The Supreme Personality of Godhead has immense varieties of potencies, and they act in different gross and subtle ways.
It is by such powerful potencies that the universe is created, although grossly it appears to be no more than the five elements—earth, water, fire, air and ether. Similarly, the bodies of all species of living entities, whether human beings or demigods, animals or birds, are also created by the same five elements, and by sexual union they expand into more and more living entities. That is the way of creation, maintenance and annihilation. One should not be disturbed by the waves of material nature in this process. Dhruva Mahārāja was indirectly advised not to be afflicted by the death of his brother because our relationship with the body is completely material. The real self, spirit soul, is never annihilated or killed by anyone.