Bjorn Ironside

Development as a warrior and leader
He joins the Great Heathen Army led by his brothers to avenge Ragnar's death.
He participated in the victory over Northumbria and in the battle against Wessex, where the Viking forces managed to disorient and force the English to retreat.
He chooses the freedom to explore the Mediterranean, which leads him to plan his own great foray into the sea.

Origins and family: He was the son of the famous Viking king Ragnar Lodbrok and his first wife, Lagertha. He is Lagertha's only son and Ragnar's eldest. He has four younger brothers: Hube, Hvitserk, Sigurd, and Ivar.

Growth and ambition
Season 4 marks a turning point in Björn's development as a character, where his growth as a warrior is solidified through battles and his ambitions of exploration.
He becomes a central figure, leaving behind his past as Ragnar's son and taking on a leadership role that propels him into the future.

Personal conflicts
Her personal life becomes complicated as she deals with her relationship with Torvi, which evolves from a complex alliance into true love.
The season culminates in a family tragedy when he witnesses the murder of his brother Sigurd by Ivar, leaving him shaken.