Onyx Storm Spice Level: 4/5, With Sources and Content Notes

The Onyx Storm spice level is 4 out of 5 on the FaeShelf spice scale: open door, with a handful of explicit scenes. That placement comes from two public sources, Common Sense Media's review and Rebecca Yarros's own content notes, both checked on October 9, 2026.

TL;DR: Onyx Storm, book 3 of the Empyrean series, is a 4/5. Common Sense Media rates its sex content "a lot", counts "a handful of sex scenes" and gives the book a 17+ age rating. The author lists on-page sexual activity, war, blood, intense violence and poisoning in her content notes. Fourth Wing and Iron Flame sit in the same band.

Onyx Storm spice level (quick answer)

Onyx Storm is a 4 on our 0 to 5 scale. A 4 means several explicit scenes that are a notable part of the book, without sex being the center of the story. Common Sense Media describes "a handful of sex scenes" with explicit detail, and Rebecca Yarros's content notes include "sexual activities that are shown on the page".

romance.io's steam rating is the usual reference for this question. Its pages returned an error when we tried to load them on October 9, 2026, so this guide relies on the two sources above and says so.

Key Takeaways

• Spice: 4 out of 5, open door. Same band as Fourth Wing and Iron Flame.
• Age rating: Common Sense Media says 17+. Fourth Wing gets 16+ from the same site.
• Content notes from the author: war, battle, blood, intense violence, brutal injuries, death, poisoning, graphic language and on-page sex.
• Book facts: first published January 21, 2025 (US), 544 pages in hardcover, 4.22 on Goodreads from about 1.96 million ratings as of October 9, 2026.

Overview: how we rate Onyx Storm

Cover image: Entangled: Red Tower Books, via Open Library

Onyx Storm is book 3 of the Empyrean, per Rebecca Yarros's Onyx Storm page. Red Tower Books, an imprint of Entangled Publishing, publishes the series in the US, and Hachette UK lists the UK edition as on sale 21 January 2025, the same day. Hachette calls it "the jaw-dropping third book in the record-breaking, multi-million-copy bestselling empyrean series". On Goodreads it won the 2025 Choice Award for Readers' Favorite Romantasy.

FaeShelf does not rate spice from memory, and we have not read the book for this page. The scale runs from 0 (closed door) to 5 (frequent, very explicit scenes central to the story). We take a published description of the sexual content, quote it, and place it on that scale. For Onyx Storm the description comes from Common Sense Media's Onyx Storm review, which marks "Sex, Romance & Nudity" as "a lot", says "a handful of sex scenes feature full penetrative sex", and adds that "characters talk a lot about desiring their partners".

A handful is several, not constant. That is the line between a 4 and a 5 on our scale, and it is why the Onyx Storm spice level lands at 4.

Step-by-Step: check the Onyx Storm spice level yourself

You can verify every part of this rating in a few minutes. These are the pages we used, in the order that gives the clearest picture.

1. Read the author's content notes. Rebecca Yarros posts a content note list on each Empyrean book page. For Onyx Storm it names war, battle, hand-to-hand combat, perilous situations, blood, intense violence, brutal injuries, death, poisoning, graphic language, and "sexual activities that are shown on the page". That last phrase answers the open door question on its own.

2. Read Common Sense Media's sex section. The review is written for parents, so it is blunt about content without quoting scenes. Look for the "Sex, Romance & Nudity" rating ("a lot" for all three novels) and the age rating (17+ for Onyx Storm).

3. Check romance.io if it loads for you. romance.io collects reader steam ratings and tags. It is a reader-sourced number, so treat it as a second opinion, and note the date you checked.

4. Compare with the earlier books. If Fourth Wing and Iron Flame were fine for you, Onyx Storm is in the same range. If you skipped scenes in those, expect to do the same here.

5. Read reader threads for chapter-level detail. FaeShelf does not list spicy chapter numbers because no publisher or review source we could verify lists them. Reader communities such as r/fourthwing discuss them openly; mark them as reader claims, not facts.

GODEEPER: Where Onyx Storm sits in the series, and when to read the new Threshing Day collection. Empyrean Series Reading Order: All Books and Threshing Day →

Onyx Storm vs Fourth Wing and Iron Flame spice

The three novels sit close together. Common Sense Media rates all three "a lot" for sex content, and the differences are in age rating and in how often the scenes appear.

Image: FaeShelf chart built from Common Sense Media reviews, checked October 9, 2026

Fourth Wing is the mildest of the three by this measure. Common Sense Media goes as far as saying that "with slightly less-explicit sex scenes, Fourth Wing could have been marketed as YA". For Iron Flame, its reviewer called the sexual content "explicit, descriptive, and over done", and the Daily Mail line on Hachette UK's Iron Flame page says "all-around sexiness" is "still sky-high".

So the Onyx Storm spice level is not a jump from book 2. It stays at the level Iron Flame set. If you want a book-by-book order with release dates, our romantasy series reading order guide covers the Empyrean alongside other big series.

Tips: content notes beyond spice

Spice is one part of the content picture, and for Onyx Storm it may not be the heaviest part. Common Sense Media flags "a fair amount of strong, bloody violence", and the author's own list includes brutal injuries, death and poisoning.

A few practical notes:

• Violence is constant. The book is set during a war, and the content notes put war, battle and intense violence first. Readers sensitive to injury detail should weigh that more than the spice.
• Language is strong. Both the author ("graphic language") and Common Sense Media flag frequent swearing.
• Skipping is possible. Several readers in a May 2026 r/fourthwing thread said the story works without the scenes. One reader wrote: "I literally skipped the spice scenes (makeouts not included) and enjoyed the story heaps."
• Threshing Day is a different case. The new collection of thirteen stories came out September 29, 2026. Hachette UK says it is best read after Onyx Storm "due to contained spoilers". We have not found a published spice description for it yet, so we do not rate it.

GODEEPER: Looking for something with the same dragons and war-college setting at a lower or higher heat? Books Like Fourth Wing, Sorted by What You Loved →

What readers say about the spice

The r/fourthwing community has argued about the spice since book 1. In a May 2026 thread titled "The Empyrean without spice", the top answer said the series would hold up without it:

The comment reads: "It would hold up without the spice, but the spice adds an extra dimension. It isn't over the top and isn't in every chapter." Another reader in the same thread liked that "the romance is directly connected to the plot. It's not just a fun addition or subplot."

Those are reader opinions, not a rating. They fit the sourced picture, though: explicit scenes that matter to the romance, spread out rather than in every chapter.

Cover image: Entangled: Red Tower Books, via Open Library

Our take

This take uses only the sources cited above. Onyx Storm is a solid 4: open door, explicit, but not a book where the sex is the plot. If Fourth Wing's level worked for you, Onyx Storm will too, and the bigger adjustment may be the violence, which both the author and Common Sense Media put front and center. Teens under 17 are outside the age rating Common Sense Media gives it. What we would still like to see is a dated romance.io steam rating, and we will add it to this page once we can load it.

The series is not finished. Yarros wrote in July 2026 that she is "writing book four", and she has described the Empyrean as "a five-book series". Prime Video has ordered a TV series, with no premiere date announced.

Frequently Asked Questions

How spicy is Onyx Storm? Onyx Storm is a 4 out of 5 on the FaeShelf spice scale. Common Sense Media rates its sex content "a lot" and describes "a handful of sex scenes" in explicit terms. Rebecca Yarros's own content notes confirm sexual activity is shown on the page, so it is open door.

Is Onyx Storm OK for teens? Onyx Storm is an adult fantasy romance, and Common Sense Media rates it 17+ for explicit sex, frequent strong language and "a fair amount of strong, bloody violence". The same reviewer rates Fourth Wing 16+ and Iron Flame 17+, so the age bar rises slightly after book one.

Does Onyx Storm have content warnings? Yes. Rebecca Yarros lists war, battle, hand-to-hand combat, perilous situations, blood, intense violence, brutal injuries, death, poisoning, graphic language and on-page sexual activity on her Onyx Storm page. The same content note list appears on her pages for Fourth Wing and Iron Flame.

Is Onyx Storm spicier than Iron Flame? Not by much. Common Sense Media rates both "a lot" for sex content and both 17+, describing sex "a handful of times" in Iron Flame and "a handful of sex scenes" in Onyx Storm. FaeShelf places both books at 4 out of 5 on its spice scale.

Is Onyx Storm closed door or open door? Open door. The author's own content notes include "sexual activities that are shown on the page", and Common Sense Media describes the scenes in explicit detail. Some readers in r/fourthwing say they skip those scenes and still enjoy the story, and one notes they are not in every chapter.

Related Reading

• Completed romantasy series you can binge: finished series only, for readers tired of waiting on book four.
• Best romantasy books of 2026: this year's big releases with dates and sourced spice notes.
• Romantasy tropes guide: enemies to lovers, fated mates and the other tropes behind the Empyrean.

References

• Rebecca Yarros: Onyx Storm page and content notes
• Common Sense Media: Onyx Storm review
• Common Sense Media: Iron Flame review
• Common Sense Media: Fourth Wing review
• Goodreads: Onyx Storm (rating checked October 9, 2026)
• Goodreads: Iron Flame
• Goodreads: Fourth Wing
• Hachette UK: Onyx Storm
• Hachette UK: Iron Flame
• Hachette UK: Threshing Day
• Marie Claire: the Empyrean series guide
• About Amazon: Prime Video orders a Fourth Wing series
• r/fourthwing: The Empyrean without spice