Sigurd Ring was a legendary 8th-century Scandinavian king, father of Ragnar Lothbrok, known for uniting Swedish and Danish lands after defeating his uncle Harald Wartooth at the mythical Battle of Brávellir, becoming a pivotal figure whose legacy set the stage for the Viking Age, though his historical existence is debated, appearing mainly in sagas as a warlord and precursor to Ragnar's fame.

Key Characteristics & Legends:
Great Warlord: He's portrayed as a formidable warrior who united vast territories in Sweden and Denmark, ruling a significant realm.
Battle of Brávellir: A major saga event where he defeated the aged King Harald Wartooth, a battle described with thousands of warriors, berserkers, and shieldmaidens.
Father of Ragnar Lothbrok: Sigurd Ring is famously known as the father of the even more legendary Ragnar Lothbrok, making him a foundational figure in Viking lore.
Precursor to the Viking Age: His reign and victory at Brávellir are seen as ushering in the era of Viking expansion, a "prologue to the Viking golden age".

Historical Context:
Saga Figure: While prominent in sagas like Sögubrot af nokkrum fornkonungum, historians debate if he was a real person or an amalgamation of historical figures.
Inspiration: He might be inspired by real warlords or figures from the Frankish Merovingian dynasty, linked to the origins of Viking expansion.

In essence, Sigurd Ring is depicted as a powerful king and unifier, a legendary figure whose mythical deeds and lineage (especially as Ragnar's father) significantly shaped Norse sagas and legends.