|Bugger their flag... If I'm on board carrying out an inspection, then this is Redania.|
|- Blood of Elves, pg.185 (U.K. Edition)|
Olsen was a Redanian customs officer whose unit regularly patrolled and boarded ships around the Temerian-Redanian border to make sure nobody was smuggling illegal goods in and to pay taxes on imported goods.
While he served Redania, he was actually from Vengerberg, Aedirn and often thought of home. He was also a veteran of the First Northern War against Nilfgaard and planned to join the Special Forces of King Demavend.
In 1266, he became friendly with Geralt, who had been on multiple trips on the barge passing his inspection site, after being hired to kill a monster that'd pulled customers off the ship earlier. On one such round, the two sat with Boatbug, the ship's captain, and Linus Pitt, an Oxenfurt Academy lecturer, during one of the inspections, sharing drink and snacks while they talked about the monster and their lives in general. However, Olsen, still being on the job, regularly had to intervene when some of the people refused to pay taxes on the goods they were bringing to sell and threatened to confiscate all the fox skins one dwarf had if he didn't pay the full amount.
When the conversation turned to Acorn Bay, Olsen informed Geralt that some Temerian guards had been asking about the witcher and something felt off to the customs officer, especially when they tried to make it sound like the witcher had an indecent relationship with an underage girl supposedly traveling with him. When Geralt learned the "guards" were acting on behalf of a man named Rience, he stated he was getting off at the bay, much to Olsen's annoyance, but before more could be said a ship flying the Temerian flag approached and boarded. Despite Geralt asking Olsen not to get mixed up in his business, Olsen knew it was unlikely they were real guards and they'd kill Geralt the moment they were far enough away.
When the guards proclaimed they were there to arrest Geralt, who stepped forward, Olsen intervened, pretending to have already arrested the witcher for smuggling and they could all settle this matter back in Oxenfurt. When he further pressed the guards for a warrant, they got silent before their leader tried to have the boat searched, hoping to find Ciri, but Olsen was unperturbed. Realizing their hoax was up, when an annoying boy, Everett, recklessly popped up next to the leader to make a comment, the man grabbed and took the boy hostage. Olsen and his men pulled out their weapons, though Geralt asked Olsen once more not to interfere before offering to be tied up. Just as they moved to tie up the witcher though, the monster, an aeschna, attacked. In the commotion, Olsen and his men proceeded to take out many of the guards with help from the dwarf he'd been arguing with earlier, who he then declared to give back all his money for being such a great shot. When they went to try and fish out the leader though, another aeschna nearby killed the man and while Olsen recited a small send off for the dead, Geralt noted he didn't bother taking his hat off.