Ferus Olin is a human Jedi padawan, apprenticed to Siri Tachi, created by Jude Watson for the Legends young-readers series Jedi Quest. He débuts in the first book, The Way of the Apprentice (Scholastic, 2002), on a mission to evacuate Radnor that fields four master-and-padawan teams at once.
His function in Jedi Quest is to be everything Anakin Skywalker is not: disciplined, correct, popular, effortlessly good at the parts of Jedi training Anakin resents. Watson is careful not to make him smug, which is what makes the rivalry work — the books are honest that Ferus is genuinely the better Jedi and that this is not the same as being the more interesting person.
He leaves the Order before the Clone Wars, and Watson brought him back as the lead of The Last of the Jedi (2005–2008), a ten-book series set in the immediate aftermath of Order 66, in which an ex-Jedi with no Order to belong to organises resistance on Bellassa and hunts for survivors. It is one of the more interesting things Legends did with the Purge, and it did it in the children's line.
None of it is current canon. Ferus Olin is a Legends character in the fullest sense: he exists to fill a space — what the Purge looked like from below — that canon has since filled with entirely different people.