He is a deformed, short hunchback with a bad temper who is always described as incredibly dirty (as Polgara states "He hates his deformed body, so he ignores it"). However, his outside appearance and temperament hides an incredibly intelligent mind, and a great eye for beauty. His original name was Din: the "Bel" prefix was added when he became one of the disciples of Aldur. His favorite animal form is that of a blue-banded hawk, with bands of "electric blue", a bird which he created because "he didn't like the regular colors". He is very good friends with Belgarath, although the two argue frequently (however, it is mentioned in The Belgariad that they both enjoy these arguments tremendously) Throughout all the stories he is seen to be very close to Polgara, this is attributed to the fact that after Polgara's mother "died" Beldin became a surrogate parent to her. And even though they constantly strive to insult each other, such is explained by the fact that both see compliments as lies considering Beldin's appearance. They rather show their affection for each other by trying to invent such elaborate insults. This is discussed by Ce'Nedra and Polgara at the beginning of Magician's Gambit. At the end of The Malloreon, he (probably permanently, although this is not specifically stated) turned himself and a Nadrak dancer who fell in love with him into birds, and flew away with her. The girl's name is Vella, a Nadrak girl he bought from Silk's partner Yarblek.
Beldin is generally considered the most intelligent and learned of the disciples of Aldur, which quite possibly places him as one of the, if not the, smartest (non divine) person in the entire series. He has been known to enjoy arguments with the other disciples of Aldur which have gone on and off for centuries at a time and was the first of the Disciples to figure out how to change into non-human forms. He also is a powerful Sorcerer in his own right, but it is not generally thought he is as powerful as Belgarath (though events in 'Enchanters End Game' appear to suggest his outmatches Polgara in raw power, or at least endurance).
When Beldin stumbled upon the Vale of Aldur, he had already learned the secret to the art of sorcery, a fact that annoyed Belgarath intensely. When Beldin was accepted as a disciple, his brothers (fellow Disciples) built an incredibly beautiful tower for him as a way to show their love, almost in an attempt to make up for his being born deformed.
Although he has an intense dislike for most Angaraks, he particularly hates Torak's last disciple Urvon. Urvon is incredibly scared of Beldin, as Beldin nurses a desire to rip out his guts with a white-hot hook, and finds enjoyment in frightening Urvon. He occasionally kills Grolim priests in Urvon's center of power, Mal Yaska, to further frighten him. Beldin's description is posted on trees all around Mal Yaska, with a sizable reward promised for his capture. Interestingly, Beldin's campaign of terror on Urvon kept the man so frightened that he didn't leave his home city for thousands of years, greatly reducing the effect Urvon could have in the world.
Beldin is named in the prophecies, however he had no formal involvement in any of the 'Events' of the Malloreon . However he is still permitted to join the others at "the place which is no more" in order to offset (in numbers only) the presence of one who is beyond the prophecies (which could be the demon Mordja, summoned by Zandramas, the then Child of the Dark).