Ur

An ice mage of incredible skill, Ur was the teacher of Gray and Leon, as well as mother to Urtear. She sacrificed her body to freeze the demon Deliora, and thus, is no longer alive.

Ur's power was so great that it is said she could have been one of the Ten Great Holy Mages.

Garuna Island Arc
During the Garuna Island Arc, it is learned from flashbacks that Gray and Leon had a teacher. After she lost her daughter when her husband left her she went to live to the mountains. Leon was her first pupil, but after Gray's home and town were destroyed by Deliora, she took him in as her second. After some difficulties, the two began to bond and Ur saw both Leon and Gray as her own children. Some believe she took them in to replace her "dead" daughter, but she denies this.

When Gray ran off to defeat Deliora on his own and avenge his parents, Ur intervened and used the Iced Shell ability to seal Deliora forever. Since Leon was unconscious, she made Gray promise to tell Leon that she was dead, though her body was just becoming ice. She believed that Leon would try to unfreeze her so he could fight her and emerge victor (his lifelong goal).

Eventually, during the present day, Leon succeeded in unfreezing Deliora with the Moon Drip, and Ur's ice body melted into the sea, where she continues to watch over her pupils.

Later, it was also revealed that her daughter is still alive, and she thought of her mother as weak.