Intensive Tantra Study and Practice
Soon after this, Tsongkhapa did his first major tantric retreat. That was Chakrasamvara according to the Kagyu tradition. And he meditated intensely on the six teachings of Naropa and gained great realization. Also the six teachings of Niguma; that’s another type of teaching.
So by now he was 34 years old, and he decided that he wanted to engage in intensive study and practice of all four classes of tantra. He said you can’t really appreciate the anuttarayoga highest class of tantra, how special it is, if you haven’t really a thorough study and practice of the other classes of tantra. So he did that. This is actually quite rare. If you look at the modern masters, it’s only people like His Holiness and his teacher Serkong Rinpoche, and so on, who really are masters of all four classes. Usually they just do a little bit of the first class (kriya tantra) and then the highest class (anuttarayoga tantra). And then he also studied further the complete stage practices (rdzogs-rim) of Guhyasamaja and Kalachakra—things he kept on studying over and over again.