How to Recruit Jubilost
You can find Jubilost at the Ford Across Skunk River area during the main questline Troll Trouble - Renowned Explorer.
Another character who joins the party late and has a... less than stellar personality. Jubilost - as if you didn't know the name already - is a world famous adventurer and writer, currently exploring the Stolen Lands and critiquing a certain fledgling baron(ess). If you play your cards right and help save his worldly possessions from a predictably bad combination of goblins and river, he'll grace your barony with his unsurpassed talent and intellect. Like Ekundayo, he'll join the party as a 5th level Alchemist.
Alchemists are good for two things; throwing bombs and casting spells. In fact, if you think of them as a Bard who throws bombs and use mutagens instead of performing Bardsong, you're not too far off. While his bombs are limited, he will get a fair variety of them (depending a bit on your feat choices as you level up). Given his high natural Intelligence, his bombs and spells will both be bolstered quite a bit. His low Strength precludes him from melee combat, however, and he's strictly inferior to Linzi as an archer. Otherwise, you can consider the two to fill roughly the same niche in your party.
He joins the party invested in several skills: Trickery, Knowledge (World), Perception and Use Magic Device. Considering his Wisdom, one has to question his usefulness as far as Perception goes, but he'll do passably well with Trickery and will excel at Knowledge (World)... and Knowledge (Arcana), should you feel inclined to invest in it. As far as serving as your rogue, however, both Linzi and Octavia will do a better job.
Jubilost makes a passable support caster who doesn't quite bring all the skills to the table you'd get with Octavia and Linzi. Still, the usefulness of his bombs shouldn't be overlooked, allowing him to contribute significantly in a fight even after the initial spell buffs are cast.