Raynar Thul is a human Jedi trainee introduced in Young Jedi Knights: Heirs of the Force (1995), the son of an enormously wealthy trading family, born aboard the family ship Tradewyn. In the early books he is the cast's snob — loud robes, family money, a rival to the Solo twins before he is a friend.
What Legends did with him afterwards is genuinely strange and one of its better swings. Presumed dead in the Yuuzhan Vong war, he is found years later in Troy Denning's Dark Nest trilogy, having been rebuilt by the insectoid Killiks into the node of a hive mind — no longer entirely a person, no longer entirely not one, and still, in some fashion, a Jedi. It is the most science-fictional thing the Expanded Universe ever did to a member of the main cast.
Catalogue entry. This figure has a verified record here rather than a full write-up — the encyclopedia labels its own depth instead of padding it.