The Supreme Personality of Godhead is the creator of the material world. There are three processes in creation — namely creation, maintenance and finally annihilation. During the period of annihilation, at the end of each millennium, the Lord becomes angry, and the part of anger is played by Lord Śiva, who is therefore called Rudra. When the Lord appeared in great anger to kill Hiraṇyakaśipu, everyone was extremely afraid of the Lord’s attitude, but Lord Śiva, knowing very well that the Lord’s anger is also His līlā, was not afraid. Lord Śiva knew that he would have to play the part of anger for the Lord. Kāla means Lord Śiva (Bhairava), and kopa refers to the Lord’s anger. These words, combined together as kopa-kāla, refer to the end of each millennium. Actually the Lord is always affectionate toward His devotees, even though He may appear very angry. Because He is avyayātmā — because He never falls down — even when angry the Lord is affectionate toward His devotees. Therefore Lord Śiva reminded the Lord to act like an affectionate father toward Prahlāda Mahārāja, who was standing by the Lord’s side as an exalted, fully surrendered devotee.