Olorin/Gandalf. Olórin, being the wisest of Manwë's maiar, was sent to aid the last of the free peoples of Middle Earth in the third age. He was sent in the form of an old man wizard, who was called Gandalf.
Melkor turned to evil...and after the poisoning of the Two Trees and the theft of the Silmarils, he fled from Valinor. He was no longer counted among the Valar, and Fëanor, one of the leaders of the Noldorin Elves, called him "Morgoth Bauglir", The Great Enemy, by which name he was known in Middle-earth ever after. He was cast out of Arda at the end of the War of Wrath.
Mandos is described as being stern and dispassionate and never forgetting a thing. He was the Vala who cursed the Ñoldor leaving Aman, and counselled against allowing them to return. But unlike Morgoth, his Dooms are not cruel or vindictive by his own design. They are simply the will of Eru, and he will not speak them unless he is commanded to do so by Manwë. Only once has he been moved to pity, when Lúthien sang of the grief she and her lover Beren had experienced in Beleriand.