Gandalf, the Grey

First known as Olorin, he was one of the Ainur who chose to come down to Middle Earth. There he interacted with the Children of Illuvitar for the long years of the @WAR OF THE SIMARILS his work focused around the Elves .
At the start of the 3rd Age he was chosen as one of the Istari , or wizards, who were sent back to Middle Earth to assist its inhabitants in their battle with Sauron . There he worked as a wandering wise man assisting Elves , Dwarves , and Humans in their struggle against the shadow.