[Empress Matilda, from "History of England" by the monks of St. Albans, 15th century]
[Source: Wikimedia Commons]
Matilda spent the next 11 years learning statecraft and assisting her husband. She acted as his regent in Italy for several years and probably participated in the Council of Worms in 1122.** She was crowned Holy Roman Empress in 1117 by Maurice Bourdin.*** The couple had no children and when the Emperor died in 1125, the Empress returned to her father.
Five years earlier, her only legitimate brother William had died, leaving Henry I without a male heir. In 1127 Matilda’s father persuaded her to marry Geoffrey of Anjou, both in the hopes that the union would give him an heir and in order to secure the border between Normandy and Anjou. Unfortunately, Matilda and Geoffrey got on badly. Even so, their first son was born in 1133.
Henry required his nobles to swear loyalty to Matilda as his heir. The nobles themselves were displeased with the idea, relations with Anjou having been antagonistic to say the least. When Henry died in 1135, his nephew Stephen of Blois seized the throne. In 1139 Matilda invaded England, leaving Geoffrey behind in Anjou.
[Seal of Empress Matilda, before 1167, source: Wikimedia Commons]
After this, affairs degenerated into a stalemate as neither side managed to gain an advantage. Matilda began spending more of her energies on her Norman possessions as her son Henry grew old enough to lead.*** In 1153 a truce was brokered and Stephen recognized Henry as his heir.
Matilda spent the rest of her life involving herself in Norman affairs and advising her son on policy. She died in 1167 and was buried at Bec Abbey.
*The future Henry II.
**This was the end of the Investiture Controversy, when Henry V gave up his right to invest bishops.
***Then only a papal envoy, he would later become Antipope Gregory VIII.
Bradbury, Jim. Stephen and Matilda: the Civil War of 1139-1153. Stroud, UK: The History Press, 2009.
Chibnall, Marjorie. "The Empress Matilda and her Sons." In Medieval Mothering, edited by Bonnie Wheeler and John Carmi Parsons, 179-294. New York: Routledge, 1996.
Matilda, Empress, Queen of the Romans - Epistolae
Empress Matilda - Wikipedia
Note: Marjorie Chibnall's book The Empress Matilda: Queen Consort, Queen Mother and Lady of the English is also a good source. I was, however, unable to get access to a copy.