A descendant of the famous Oxenstierna family, Björn lives a quiet life with his parents in Stockholm. Growing up, his stern appearance and introverted personality made it difficult for him to make friends his own age so he engaged himself with Pokemon instead. His first Pokemon was a Snover that he found the woods during a family trip, and it serves as his main Pokemon as an Abomasnow. Björn got his start playing in local tournaments when he was 12 years old and later expanded to other parts of Northern Europe by his mid-teens.

Trainers are intimidated by Björn and are often frightened to fight him. Many believe he has a team with some of the strongest and scariest Pokemon around, but are immediately thrown off-course when he sends out his Blissey or Togekiss (which he finds amusing). His Pokemon are actually quite friendly and love to be around others. Although he's a top trainer in his home country, he leads a very private life compared to others at his level. Björn adores children and wants to be a teacher or run a Pokemon daycare one day.