Complex sentence: The character is based on the Anglo-Saxon myth of Bēowulf as depicted in the Nowell Codex also known as the "Beowulf manuscript", a document of unknown provenance authored sometime between the 8th and 11th centuries.
Split into simpler sentences: The character is based on the Anglo-Saxon mythic hero Bēowulf, as depicted in the Nowell Codex also known as the "Beowulf manuscript". The Nowell Codex is a document of unknown provenance authored sometime between the 8th and 11th centuries.