Olorin

'Wisest of the Maiar was Olórin. He too dwelt in Lórien, but his ways took him often to the house of Nienna, and of her he learned pity and patience.

Of Melian much is told in the Quenta Silmarillion. But of Olórin that tale does not speak; for though he loved the Elves, he walked among them unseen, or in form as one of them, and they did not know whence came the fair visions or the promptings of wisdom that he put into their hearts. In later days he was the friend of all the Children of Ilúvatar, and took pity on their sorrows; and those who listened to him awoke from despair and put away the imaginations of darkness.'

JRR Tolkien: The Silmarillion: VALAQUENTA: Account of the Valar and Maiar according to the lore of the Eldar