Styrbjörn Starke (the Strong) was a legendary 10th-century Swedish prince, nephew of King Eric the Victorious, known for his fierce, warlike nature (hence "Styr-," meaning forceful or restless) and violent temper, who was exiled and became a famous Viking sea-king, leading the elite Jomsvikings before being defeated and killed by his uncle at the Battle of Fýrisvellir while trying to claim the Swedish throne. He was a powerful, ambitious warrior who defied authority, gathered formidable forces (including the Jomsvikings), allied with Denmark's Harald Bluetooth, and, despite his ultimate defeat, achieved a form of immortality in legend and stone as a symbol of defiance.

Key Characteristics & Story:
Origin: Son of Swedish King Olof, given the name "Styrbjörn" (Forceful Bear) by his uncle Eric due to his unruly disposition.
Violent Nature: Known for being big, strong, and quick to anger, even killing a courtier as a youth.
Exile & Sea-King Career: Denied co-rule, he was given ships by Eric and became a formidable Viking raider, taking control of the feared Jomsvikings.
Danish Alliance: Married Thyra Haraldsdóttir, daughter of King Harald Bluetooth.
Clash with Eric: Returned to Sweden to seize the throne, leading his forces (including Jomsvikings) against Eric at the Battle of Fýrisvellir.
Defeat & Immortality: Though he fought fiercely, Eric sacrificed to Odin, turning the tide; Styrbjörn fell, but his legend lived on, even being commemorated on runestones.

Legacy: Styrbjörn embodies the classic Viking saga figure: a powerful warrior whose ambition led to a glorious, albeit doomed, challenge against established power, securing his place in Norse lore as a symbol of fearless, uncompromising strength.