Karlsson is a SwedishPikeman and one of the Heroes in With Fire & Sword. He likes Priest Spasokukotsky, dislikes Algirdas and Tepes, is liked by Fatima, is disliked by Oksana and Victor De La Buscador, and disapproves of heavy losses, unpaid wages and starvation. He also dislikes fighting his own people as he says after telling his story, but is not confirmed if he will say anything if you are fighting the Swedish. Due to his high polearm skill, he is good as a pikeman or lancer, especially with the Hussar Lance. He identifies religiously as Lutheran, as noted in-game when he explains why he likes Priest Spasokukotsky.
"I served in the musket regiment of General Lennart Torstenson's, the finest commander in all of Sweden. I took part in the battle of Jankau, where we utterly defeated the very best of the German forces! Ah, those were the days!"
"Our regiment was given leave in a prosperous town of Great Poland. We soldiers of His Majesty, King Carl, allowed ourselves to relax a little. And the tale that I sold my halberd to a trader is but a blatant lie! I mean, I can recall no such thing... Morning come, and word of it came to the regiment commander, and he relieved me of my soldier's patent. Yet I have not abandoned hope to re-enlist. I already prepared a petition, which I shall personally deliver to King Karl [sic]. However, the quarters of our august monarch moves with the army, and I squandered almost all my savings chasing after it."