Marcus Cantarius tells you that Janus Fieri at the Crossroads in Commonlands could use some help. If you accept he sends you a letter of commission to give to Janus Fieri at the Crossroads. If you haven't been there before the Crossroads are reached by heading west along the road from Freeport.
Janus will ask you to search for a book at the nomad camps in Commonlands. You can find the book as an interactive ground object at -152, -48, -828. Obtain it and give it to Janus Fieri.
Janus will then send you out to kill 10 Orc Lumberjacks in Commonlands. They can be found in the southwestern part of the zone, near the Hidden Valley entrance. Complete this and return to her for your choice of rewards.