yat sṛṣṭam idam ātmanaḥ
sanniyacchati tat kāle
tataḥ—thereafter, at the end; kāla—destruction; agni—fire; rudra-ātmā—in the form of Rudra; yat—whatever; sṛṣṭam—created; idam—all these; ātmanaḥ—of His own; sam—completely; niyacchati—annihilates; tat kāle—at the end of the millennium; ghana-anīkam—bunches of clouds; iva—like that of; anilaḥ—air.
Thereafter, at the end of the millennium, the Lord Himself in the form of Rudra, the destroyer, will annihilate the complete creation as the wind displaces the clouds.
This creation is very appropriately compared to clouds. Clouds are created or situated in the sky, and when they are displaced they remain in the same sky without manifestation. Similarly, the whole creation is made by the Supreme Personality of God in His form of Brahmā, it is maintained by Him in the form of Viṣṇu, and it is destroyed by Him in the form of Rudra, or Śiva, all in due course. This creation, maintenance and destruction are nicely explained in the Bhagavad-gītā (8.19-20) as follows:
The nature of the material world is that it is first created very nicely, then it develops very nicely and stays for a great number of years (even beyond the calculation of the greatest mathematician), but after that it is again destroyed during the night of Brahmā, without any resistance, and at the end of the night of Brahmā it is again manifested as a creation to follow the same principles of maintenance and destruction. The foolish conditioned soul who has taken this temporary world as a permanent settlement has to learn intelligently why such creation and destruction take place. The fruitive actors in the material world are very enthusiastic in the creation of big enterprises, big houses, big empires, big industries and so many big, big things out of the energy and ingredients supplied by the material agent of the Supreme Lord. With such resources, and at the cost of valuable energy, the conditioned soul creates, satisfies his whims, but unwillingly has to depart from all his creations and enter into another phase of life to create again and again. To give hope to such foolish conditioned souls who waste their energy in this temporary material world, the Lord gives information that there is another nature, which is eternally existent without being occasionally created or destroyed, and that the conditioned soul can understand what he should do and how his valuable energy may be utilized. Instead of wasting his energy in matter, which is sure to be destroyed in due course by the supreme will, the conditioned soul should utilize his energy in the devotional service of the Lord so that he can be transferred to the other, eternal nature, where there is no birth, no death, no creation, no destruction, but permanent life instead, full of knowledge and unlimited bliss. The temporary creation is thus exhibited and destroyed just to give information to the conditioned soul who is attached to temporary things. It is also meant to give him a chance for self-realization, and not for sense gratification, which is the prime aim of all fruitive actors.
Link to this page: https://prabhupadabooks.com/sb/2/10/43