Clef is a character from Magic Knight Rayearth. He lives in Cefiro, and is one of the most powerful magicians there, in fact he is the Supreme Guru of Cefiro. He has a short temper and likes things to be quiet. He also likes to talk to Seijyus (spirit beasts). He dislikes rowdiness, and hence gets angry at Umi very quickly.
Although he looks very young (even childish), Clef is 745 years of age.
Clef promised Princess Emeraude that he would help the Magic Knights. He helped them with magic, and gave them armor.
In this version of the story Clef has come to earth from Cephiro. His mission is to save the earth and help find the Magic knights with the power to wear the Mashin. He has trapped the people of earth between dimensions, and helps the knights with information as well as protecting them with his magic.
Clef is significantly taller in the OAV, and he has more hair ^_^