Complex sentence: It is held that "Kambu Swayambhuva" was a learned prince who had initially been an Indian king who had led a "digvijaya" expedition in the Far East and entered an area having jungles that was being ruled by a king of Naga lineage.
Split into simpler sentences: It is held that "Kambu Swayambhuva" was a learned prince who had initially been an Indian king. He had ventured into the Far East and entered an area having jungles that was being ruled by a king of Naga lineage.