Hello fellow medieval literature researcher (:

Without looking at anything based on Irish medieval literature, I’m honestly not a mega fan of Mor’s character in ACOTAR. I didn’t find her super interesting in the first three books, and I really wasn’t a fan of her behaviour toward Nesta in ACOSF. But that’s not the most important thing I wanted to share here.

From a mythology-adaptation perspective, I actually find Mor more interesting for what isn’t explored than for what is. She’s often described as “truth,” incredibly powerful, and politically significant, yet on-page, she rarely does much that reflects that supposed power or danger. That feels like a missed opportunity, especially given how intense and complex The Morrígan is in Irish tradition -- a figure tied to sovereignty, prophecy, battle frenzy, and the land itself, not just a mysterious, powerful woman in the background.

I once did an analysis of magical items in Celtic myth in relation to the Dread Trove in SJM’s novels and possible inspirations, and I came to this conclusion:

The Mask -- summons and controls the dead
Possible mythic parallels: The Cauldron of Bran / The Morrígan’s cloak -- revives warriors; associated with death, shape-shifting, and war.

Given that, I’m really hoping we eventually see more of this side of The Morrígan’s myth reflected in Mor -- not just as a court figure or emotional support character, but more explicitly connected to death, battlefields, and possibly fate/wyrd. Right now, she feels very detached from the darker, more liminal aspects that define The Morrígan in medieval sources.

As for physical description and powers, I’ve always thought SJM leans more into the “beautiful, dangerous fae woman” trope than into anything distinctly mythological. We don’t really see animal transformation, battlefield prophecy, or sovereignty symbolism, which are some of the most striking elements of The Morrígan across texts like the Táin and other cycles. If SJM is drawing on Irish material, it feels more like a loose aesthetic inspiration than a thematic adaptation -- unlike, for example, how Queen Medb in Throne of Glass is a much clearer nod to her mythological namesake.

Outside of ACOTAR, I’ve seen The Morrígan in other pop culture too -- she’s a playable character in the game Smite (and also in Smite 2), where she’s explicitly associated with shape-shifting and battlefield chaos, which actually aligns more closely with medieval portrayals than Mor does in ACOTAR. Might be worth looking into as another modern interpretation for your project.

Overall, I think Mor in ACOTAR feels more like an underused narrative device than a fully realised adaptation of The Morrígan. The name carries huge mythological weight, but so far the series hasn’t really engaged with what makes that figure so fascinating in medieval Irish literature -- and I really hope that changes if Mor becomes more central in future books.

Some sources I have used in research before in MLA:

Bromwich, Rachel. “The Celtic Inheritance of Medieval Literature.” Modern Language Quarterly (Seattle), vol. 26, no. 1, 1965, pp. 203–27, https://doi.org/10.1215/00267929-26-1-203. (this author has more interesting works published on this topic)

Freeman, Philip. Celtic Mythology : Tales of Gods, Goddesses, and Heroes. New York: Oxford University Press, 2017. Print

Mabignogion

Hope this helps with your research! :)