Born ‎1030 Alençon, Orne, Basse-Normandie, France, died ‎2 Dec 1079 Bures Castle, Dives, Calvados, Basse-Normandie, France‎, age 48 or 49 years
Mabel de Bellême de Talvas was the daughter of William I Talvas and his first wife Hildeburg.

When her father was exiled by her brother Arnulf in 1048 she accompanied him until both were taken in by the Montgomery family.

Between 1050-1054 she married Roger II de Montgomery, later 1st Earl of Shrewsbury.

Mabel inherited the Bellême honour in 1070 at the death of her uncle Yves, Bishop of Séez and Lord of Bellême.

As to her character:
Of all of Orderic’s female subjects, Mabel was the most cunning and treacherous; if not entirely for her own misdeeds then as the mother of Robert de Bellême, who had a reputation for savagery as well as cruelty. In one passage Orderic describes her as "small, very talkative, ready enough to do evil, shrewd and jocular, extremely cruel and daring."

In perpetuating her family’s feud with the Giroie family, Mabel set her sights on Arnold de Echauffour, the son of William fitz Giroie who her father had mutilated at his wedding celebration. She obtained part of his estates when she and her husband Roger convinced Duke William to confiscate his lands.
In 1063, however, Arnold was promised forgiveness by the Duke, and was to have his lands restored. To prevent this, Mabel plotted to kill Arnold. She attempted to murder Arnold of Echauffour by poisoning a glass of wine but he declined to drink.
Her husband's brother, refreshing himself after a long ride, drank the wine, and died shortly thereafter.
In the end, though, she bribed Arnold's chamberlain, providing him with the necessary poison, this time being successful.

Excepting Theodoric, abbot of the abbey of Saint-Evroul, who she listened to at times, Mabel was hostile to most members of the clergy; but her husband loved the monks at Saint-Evroul so she found it necessary to be more subtle.
In an incident in 1064, she deliberately burdened their limited resources by visiting the abbey for extended stays with a large retinue of her soldiers.
When rebuked by Theodoric the abbot for her callousness she snapped back that the next time she would visit with an even larger group. The abbot predicted that if she did not repent of her evilness she would suffer great pains and that very evening she did. She left the abbey in great haste as well as in great pain and did not abuse their hospitality again.

Mabel continued her wickedness, causing many nobles to lose their lands and become destitute. In 1077 she took the hereditary lands of Hugh Bunel by force.
Two years later while coming out of her bath, she was killed by some men who had crept into the castle. Hugh had enlisted the help of his three brothers, gained entry to the castle of Bures on the Dives and struck off her head with his sword.

Mabel's murder occurred on 2 December 1079 and she was buried three days later at Troarn.