This is a lion also called "The many Colored Death" who is living in the desert of Goab, the desert of colors. It's the most dangerous character in all Fantasia, so no one can approach him. Only Bastian who wore the Auryn have met him. He know many secrets of Fantasia. During the day, he spent all is time alone in the desert, and dies every nightfall. 

Note: It's not a character from the movie. Only from the Michael Ende Novel.