Halt's actual entrance to Araluen and subsequent adventures saving the Kingdom from Morgarath is well documented. The implied life through the main series is not. This is a recreation of what may have been.
Halt was going to become the king of Clonmel, until he was fed up with assassination attempts. According to 'The Hibernian,' he originally came to Araluen with the hopes of finishing his apprenticeship, but the Corps had been slowly dismantled over nearly a decade by Morgarath. The prologue to 'The Ruins of Gorlan' neither confirms nor denies whether the original intention was that Rangers were dismantled, Pritchard escaping to Hibernia, focusing instead on the plot to use Wargals and attack in the confusion after King Oswald's death. Pritchard is also not mentioned as a motivating factor to escape to Araluen and become a Ranger in 'The Kings of Clonmel.' Halt may have had an 'in' with Duncan, both being royals, or simply fell in love with the Ranger life after a coincidental meeting with one.
Either way, Halt ended up in Araluen and started and/or finished his apprenticeship. He became a highly respected Ranger assigned to Redmont Fief and made friends with Average Ranger Crowley—Halt's oldest friends are Crowley and Arald ('The Icebound Land'). Crowley has been in the Corps for at least 30 years by 'The Sorcerer in the North,' meaning he could have been Halt's senior and Halt's mentor—Gilan and Will both like to annoy Halt as former apprentices like Halt enjoys annoying Crowley ('The Ruins of Gorlan'). At some point Halt rides with the Temujai long enough to steal some horses, learn the tongue, and borrow the idea of a recurve bow.
Morgarath makes a move a decade into Halt's career as a Ranger. Halt steps up and leads the cavalry through the woods, defeating the enemy and making a bigger name for himself. At this point, his reputation is big enough, he's been a close confidant of King Duncan for 5 years ('The Icebound Land'). Sir David, father to Gilan, was in charge of tactics, and they became good friends ('The Burning Bridge').
The original Outsiders outbreak happens on Araluen's west coast, and a whole lot of Rangers fight them off. Halt continues to visit Sir David, and takes on Gilan as an apprentice, since the boy was tired of sword drills. Gilan graduates and becomes a nuisance to Halt at Ranger Gatherings. More years pass, Halt finds it in himself to become grumpier, and then the main series starts.
The general premise is similar to the prequel series, but why does Halt come to Araluen and stay as a Ranger? Who was his mentor, if not Pritchard? Was it Crowley, and that's why they're close? And what adventures has Halt gotten up to that were never covered, even in passing, by Flanagan? So many more questions are opened up.
YOU ARE READING
A Collection of Ranger's Apprentice Theories
RandomAdmired Ranger goes to Royal Dungeons for Songwriting? Beyond clickbait titles, the world of Ranger's Apprentice has heaps of theory-worthy material. This collection uncovers world-building flaws to be exploited for fanfiction moments and form a dis...