[1] The protagonist of Griffith's version is Peretur, a girl raised alone in the wilderness by her mother, who develops a magical ability to communicate with animals.

Griffith wrote Spear after being invited to contribute to an anthology of Arthurian retellings: her planned short story grew into a longer work.

[3] Peretur endures a series of challenges that bear close resemblance to stories in the Arthurian tradition, but one reviewer described her journey also as one of "understanding, of her past, of other people, and of the world".

The Chicago Review of Books wrote that Griffith "threads the needle" by incorporating queer and polyamorous characters without couching their identities in modern language,[4] while T. S. Miller of Strange Horizons praised the depiction of Llanza as a character with a limp who remained peerless in combat, as a "refreshingly casual" depiction of disability.

[4] The idea for Spear came to Griffith after she was invited to contribute to Sword Stone Table, an anthology of Arthurian retellings edited by Swapna Krishna and Jenn Northington.

[1] According to a review in Strange Horizons, the Welsh orthography of several characters' names, including Gwenhwyfar and Myrddyn, conjure a "Celtic Arthur", providing a geographic explanation for the presence of the Irish Tuath Dé.

Nimüe believes that Arturus would have spawned a line of tyrannical rulers, but allowing his lineage to die out will bring peace.

[3] Peretur treats her attraction to women as a matter of fact, and there is an implied polyamorous connection between Arturus, Gwenhwyfar, and Llanza rather than the traditional love triangle.

[3] Publishers Weekly noted that Peretur goes through a series of challenging encounters that hewed closely to stories in the Arthurian tradition.

[7] Miller writes that while Spear could be described as "the story of a crossdressing queer woman with a supernatural gift in combat" who sought to become an Arthurian knight, doing so would be a misinterpratation of the narrative.

[3] According to Miller, Peretur's childhood at first has more in common with the story of Grendel and his mother rather than many Arthurian legends; they live alone in a cave, cut off from contact with the outside world.

The review praised the novel's exploration of gender and sexuality, writing that Griffith "threads the needle" by incorporating queer and polyamorous characters without couching their identities in modern language.

[5] Writing for the New York Times, author Amal El-Mohtar similarly praised Griffith's attention to historical detail and depiction of material culture.

He drew particular attention to Griffith's use of alliteration and metaphor, as well as the use of references to stories outside the Arthurian mythos, which created an "almost effortlessly mythic" effect, which Brookins compared to the language used by Ursula K. Le Guin in the Earthsea books.

By the end of the novel, Wolfe writes that "it no longer feels at all like yet another iteration of familiar matters, but a marvelously concise epic that is entirely Griffith's own.

"[5] Brookins suggested that Griffith's use of an unconventional Welsh setting for a familiar Arthurian storyline allowed readers to focus on the specifics of her version.

[1] Publishers Weekly called the novel "an ideal pick for fans of retold legends", writing that the work cements Griffith's reputation as a "consummate storyteller".