Kamsa addressed his sister and brother-in-law as maha-bhagau because although he killed their ordinary children, the goddess Durga took birth from them. Because Devaki bore Durgadevi in her womb, Kamsa praised both Devaki and her husband. Asuras are very devoted to the goddess Durga, Kali and so forth. Kamsa, therefore, truly astonished, appreciated the exalted position of his sister and brother-in-law. Durga is certainly not under the laws of nature, because she herself is the controller of the laws of nature. Ordinary living beings, however, are controlled by these laws (prakrteh kriyamanani gunaih karmani sarvasah [Bg. 3.27]). Consequently, none of us are allowed to live together for any long period. By speaking in this way, Kamsa tried to pacify his sister and brother-in-law.