The Supreme Personality of Godhead, Visnu, is known as Yogesvara. Yatra yogesvarah krsnah. Mystic yogis want to acquire some power by practicing the yoga system, but Krsna, the Supreme Personality of Godhead, is known as the Supreme Lord of all mystic power. Lord Siva wanted to see the Mohini-murti, which was captivating the entire world, and Lord Visnu was gravely thinking of how to captivate Lord Siva also. Therefore the word bhava-gambhiram is used here. The illusory, material energy is represented by Durgadevi, who is the wife of Girisa, or Lord Siva. Durgadevi could not captivate Lord Sivas mind, but now that Lord Siva wanted to see Lord Visnus feminine form, Lord Visnu, by His mystic power, would assume a form that would captivate even Lord Siva. Therefore Lord Visnu was grave and at the same time was smiling.