Short answers, pulled from the story.
Old Saxony occupied the region between the Rhine and Elbe rivers in what is now northwestern Germany. It included the areas later known as Eastphalia, Westphalia, Angria, and Nordalbingia, corresponding roughly to the modern German federal state of Lower Saxony, parts of North Rhine-Westphalia, Schleswig-Holstein, and Saxony-Anhalt.
The name Saxon is thought to derive from the word "Sax," meaning stone knife. Ptolemy's Geographia, written in the 2nd century, is sometimes considered the earliest written mention of the Saxones, placing them north of the lower River Elbe.
Ewald the Black and Ewald the Fair were two priests from Northumbria who set out in 690 to convert the Old Saxons to Christianity. On the 3rd of October 695 at Aplerbeck, near Dortmund, both were killed by the Saxons; Ewald the Fair was quickly murdered while Ewald the Black was tortured before his death. Both are now venerated as saints in Westphalia, and a chapel still stands at the site.
Charlemagne waged a campaign against the Old Saxons from 772 to 804, a thirty-year war described as bloody and attritious. The Saxon resistance was led by Widukind. After their defeat, the Saxons were forced to convert to Christianity and their homeland was reorganized as the Duchy of Saxony within the Carolingian empire.
The Irminsul was a sacred pillar or divine tree at the center of Old Saxon pagan religion, believed to connect Heaven and Earth. It is thought to have stood at a site near modern Obermarsberg.
The Anglo-Saxons in Britain were descended from groups that migrated from Old Saxony, along with Angles and Jutes, following the collapse of Roman defenses on the Rhine in 407. The traditional date for this migration is 449, known as the Adventus Saxonum. Writers such as Bede used the term "Old Saxons" specifically to distinguish the continental Saxons from the Saxons living in Britain.