Alatar was on of the original three Istari chosen to journey to Middle-earth (the others being Saruman and Gandalf). He was chosen by Oromë.

Eventually, he took Pallando with him, as a friend. Together, they were given the name 'Ithryn Luin' (Blue Wizards) because they came dressed in sea-blue robes.

They had no names in the West of Middle-earth, and travelled into the East with Saruman. They did not return, and we do not know what happened to them.
Encyclopedia entry originally written by Hathaldir