One of the many mysteries of the Legend of Zelda series pertains to the many reincarnations we've seen of the Seven Sages. From Seven Maidens, to the Seven Wise Men, to the seven ethereal spirits, never have we seen the sages used more prominently than in Ocarina of Time. With the need for saving and 'awakening' the ancient sages in Ocarina of Time, Rauru moreso than any - even Zelda - seemed like the constant. Yet at the same time, he was the most mysterious of them all.
Rauru was the knowledgeable one. The one who recalled the times of the past when the Temple of Time was built over the ruins of the Sealed Temple, as stated in Hyrule Historia. The one who was there when the Sacred Realm was sealed away from Hyrule, with the Master Sword acting as the key. Rauru never needed Link to save him. He never appeared alongside the other sages outside of the Sacred Realm. Rauru was an enigma, but Skyward Sword seemingly had a thing or two to say on the topic, at least at first.