Willm Lywin was one of the Duinuogwuins, a species of winged, large-sized reptiles the biology and lifestyle of which was shrouded in mystery. Although the Duinuogwuin, also known as "Star Dragons," only had one sex, Lywin was always referred to as male in Galactic Basic Standard. He was born many centuries before the Great Sith War, during the height of the Old Republic, when the Holy Order of the Jedi Knights still maintained peace across the known galaxy.
Lywin himself had joined the Order, in which he was trained and attained the rank of the Jedi Knight. Within the Order, the Duinuogwuin spent several centuries acting as a "living snubfighter" whose mission was to escort a traveling praxeum ship in space. When the Jedi established a permanent academy on the planet of Teya IV, Lywin was amongst its founding fathers. Since the main buildings were too small to accommodate his gigantic size, the Duinuogwuin dwelled in the mountains that housed the Cave of Truth, a place which served as a testing ground for apprentices.
By 4000 BBY, Lywin was the last surviving founder of the Teyan Praxeum. That year, he encountered the young Vici Ramunee, who had been tasked with entering the Cave Truth as part of her Jedi Trials. Ramunee, who was accompanied by her little brother Veni, mistook Lywin for a dangerous monster and activated her lightsaber, ready to fight. The Star Dragon was amused by Ramunee's attempt to "protect" her brother, and he revealed his identity. Once the misunderstanding was cleared up, Lywin escorted the two young Jedi the rest of the way to Cave of Truth, where Vici Ramunee entered alone and emerged successful in her trials.
Because of his draconic features and tremendous size, Lywin often frightened his Human colleagues without meaning to. Those who got to know him, however, quickly realized that he was extremely affable, in keeping with the good reputation of his species as a whole.