Dark Agnes de Chastillon (also known as Agnes de Chastillon, Dark Agnes, Agnes de la Fere and The Sword Woman) is a fictional character created by Robert E. Howard and the protagonist of three stories set in 16th Century France, which were not printed until long after the author’s death.

The character of Agnes was beaten by her father and almost forced into an arranged marriage. She avoids this by killing the bridegroom and running away. She meets Etienne Villiers, who at first attempts to sell her to a brothel, and Guiscard de Clisson, a mercenary captain who trains her as a swordswoman. When de Clisson is killed, Agnes heads for Italy with Villiers.

Like the later character Red Sonja, who was based on another Howard character, Red Sonya of Rogatino, Agnes has red hair and a short temper. But while Red Sonja’s skill in the handling of swords is a divine gift, Agnes’s skill is a mixture of innate talent and training.

The character may be partially based on Novalyne Price, the American schoolteacher and writer who became close friends with, and occasionally dated, Robert E. Howard. Novalyne met Howard in 1933.

The first story (Sword Woman) was written around or a little time before Catherine Lucile Moore wrote here Jirel of Joiry stories. Howard actually sent her a copy of the manuscript for Sword Woman. Howard may have written ‘Sword Woman’ in June or July, 1934. Moore is very likely to have been inspired to write her stories about Jirel of Joiry which where published in Weird Tales (the first one in October 1934), ie. after Howard wrote his story. Fans saw her character as a female version of Conan. Moore was enthusiastic about the first of Howard’s “Dark Agnes” stories and wrote:

My blessings! I can’t tell you how much I enjoyed “Sword-Woman”. It seemed such a pity to leave her just at the threshold of higher adventures. Your favorite trick of slamming the door on a burst of bugles! And leaving one to wonder what happened next and wanting so badly to know. Aren’t there any more stories about Agnes?

Stories

Sword Woman
This is the origin story for Agnes. It features her abortive arranged marriage and subsequent training. “Sword Woman” was first published in REH: Lone Star Fictioneer #2 (Summer 1975).

Blades for France
Agnes, still with her sidekick Etienne Villiers, faces international intrigue with Cardinal Thomas Wolsey. “Blades for France” was first published in Blades for France (1975). There exists two incomplete drafts for this story. One consists of pages 1-11 of what seems to be a second draft, with chapter titles given. This draft ends shortly after the beginning of the second chapter. The other draft consists of pages 2-25 and has no chapter titles; this, and other internal evidence, suggests that it was a first draft. 

The ending of ‘Blades’ is taken from a first draft and not really “fleshed out”. Glenn Lord provided the title for the story. 

Mistress of Death
Howard only wrote two drafts of “Mistress of Death”, both incomplete. The second of the two drafts was later completed by Gerald W. Page and it was this version that was first published in Witchcraft & Sorcery Volume 1 Number 5 (January–February 1971). Gerald W. Page also provided the title. This is the only Dark Agnes story to include a fantasy element, in the form of a sorcerer. It is not written to the same standard of the two stories Howard completed, and features some departures from the established character, making her more stereotypically feminine.

It was later adapted into a Conan tale, “Curse of the Undead-Man”, appearing in The Savage Sword of Conan no. 1, 1974, where the Cimmerian encounters Red Sonja (in place of Dark Agnes).

Source: Wikipedia.

Also read this critical overview of Robert E. Howard’s Sword Woman by Jessica Amanda Salmonson. Thanks also to Patrice Louinet for information about timelines.