Rauru

Rauru is the elder Sage of Light who resides at the Temple of Light, particularly the Chamber of Sages. He's one of the Ancient Sages that actually built the Temple of Time, and also labelled Link as the Hero of Time once he grew up.

He was first seen when Link wakes up after his seven-year slumber just as soon as he drew the Master Sword from the Pedestal of Time and opened the door to the Sacred Realm. He informed him that he was too young to wield the potent blade and it wasn't his time to be the Hero of Time. Thus, the entrance to the Triforce was vulnerable, rendering Ganondorf to take it for himself. He also stated that he must find and reawaken those that would become the remaining five Sages in order to restore peace to Hyrule and banish the King of Evil. The land of Hyrule transformed into a world of monsters since Ganon possesses the Triforce. With that, he sets Link off on his journey and implores him to add the Sages might to his, just after he gifted him the Light Medallion.

He wasn't seen until much later, particularly when Link was able to awaken the Sage of Spirit, Nabooru, declaring that the battle of evil has arrived. He also assisted Link as he went to the broken entrance of Ganon's Castle, creating a rainbow bridge across the massive lava pit. By the time Ganon was defeated by the Hero of Time, he ordered all the Sages to seal away the King of Thieves. This was also done even after Link loses to Ganon, turning the Sacred Realm into the renowned Dark World.

It's also said in the Hyrule Historia that he was actually the owl, Kaepora Gaebora, who guided Link as a kid.

Ikran's Lost OoT/Pokémon crossover
Rauru was the same in the game, though he attained three Pokémon as his guardians soon after Link and Zelda II awakened all the Sages, consisting of Mew and Mewtwo alternating with each other, Girafarig, and Slowking. He was able to have them for a short while, before the Pokémon declared war. They were soon sealed away, until Link dispelled the barriers. Rauru ordered his Sages to seal Ganon away as he was successfully defeated by the Hero of Time.