Onyx Storm is the book where the Empyrean series goes fully epic. The scale expands from a war Violet barely understood to a continental conflict with stakes that make everything from the first two books look like prologue. New powers, new factions, and a Violet-Xaden relationship stretched to its most painful point. If you've finished it and now face the wait for book four with nothing to fill the space, these are the picks: books that match the combination of massive-scale fantasy war, a romance under unbearable pressure, and a world whose mythology keeps rewriting itself with every revelation.
Book three of ACOTAR is where Maas goes full war fantasy: the romantic arc that dominated the first two books has to compete with a continent-wide conflict, and the mythology that was slowly seeded across both earlier novels finally pays off in full. The experience of reading ACOWAR after ACOMAF is structurally identical to reading Onyx Storm after Iron Flame — the scale expands dramatically, new factions enter the war, and both authors use the third book to answer questions they've been hiding since book one. The Feyre-Rhysand dynamic under pressure is the closest thing romantasy has to Violet-Xaden at the equivalent moment.
The third Throne of Glass book is where Maas first figured out how to write a third installment at continental scale. Celaena's powers expand beyond what the earlier books suggested was possible, the political geography of the world opens up enormously, and the book introduces a conflict so much larger than the one it started with that it feels like a series reset. If Onyx Storm worked for you specifically because Violet's new abilities changed the math of the entire war, Heir of Fire does the same thing for Celaena and does it extremely well.
The sequel to Six of Crows raises the stakes of the heist series to something approaching war, and does what Onyx Storm does: takes a cast of people who were already operating at their limit and applies pressure from every direction simultaneously. Bardugo's plotting is dense in the best way, every character gets a meaningful arc, and the ending delivers on the slow-burn emotional investment of both books. If you loved Onyx Storm's willingness to put Violet through genuinely terrible things before the payoff, Crooked Kingdom operates the same way.
If what Onyx Storm did was make you want more epic scale — more complex magic systems, more political factions, more revelations about a world's hidden history — The Stormlight Archive is the answer. Sanderson's series is one of the most ambitious fantasy projects ever written, with a magic system built on ancient storms and abilities bonded to living weapon-spirits who are deeply individual characters in their own right. The scale is enormous, the world-building is meticulous, and Kaladin Stormblessed is one of the best protagonists in modern fantasy. Start here if you haven't.
A trilogy (now series) that escalates just like the Empyrean books do: what starts as a contained survival story becomes a solar-system-spanning revolution by book three. Pierce Brown is exceptionally good at the specific feeling Onyx Storm creates — the sense that the conflict is bigger than any individual's ability to comprehend or survive, that alliances are temporary, and that every victory comes at a cost the protagonist didn't account for. Less romance, much more brutal action, but the political betrayal layer is the most sophisticated in modern fantasy.
Nesta and Cassian are rivals-to-lovers in a spin-off set after the main ACOTAR trilogy, in a world now recovering from war. If Onyx Storm appealed to you specifically because the romance between Violet and Xaden is combative, loaded with pride and anger, and resistant to easy resolution, ACOSF is the most direct equivalent in romantasy. Maas gives Nesta a genuinely difficult personality and doesn't sand it off to make her likeable — the character work here is sharper than in the main trilogy.
If you somehow finished all three Empyrean books without reading this series, now is the time. Armentrout's Blood and Ash books escalate in exactly the same pattern as the Empyrean series: the contained forbidden romance of the first book opens up into massive world mythology by book three, and the revelations about what the world actually is fundamentally change how you understand every earlier scene. The slow-burn pacing and the morally layered love interest are both Yarros-adjacent at a very high level.
A fantasy military empire with two protagonists on opposite sides of the law, a romance that keeps being interrupted by war, and a series that grows darker and more morally complex with each installment. By book three — A Reaper at the Gates — the scale has reached the continental level that Onyx Storm operates at, and the cost of the conflict has become almost unbearable. Tahir doesn't spare her characters, which is exactly what Yarros does with Violet and Xaden in the third Empyrean book.
Maas's Crescent City series reaches its most Onyx Storm-adjacent moment by the third book — House of Flame and Shadow — where the world's complete mythology is revealed in one of romantasy's most ambitious structural moves. But start here: the first book establishes a world and a romance that the later books use as emotional leverage in the way Onyx Storm uses everything established in Fourth Wing and Iron Flame. Patience with the slow build pays off enormously by the end of the trilogy.
A gothic fantasy with a heroine who summons a demon to solve her sister's murder and ends up entangled in a war between supernatural powers she barely understands. What makes this work for Onyx Storm readers specifically is the tone: Maniscalco's world is constantly revealing itself as larger and more dangerous than the protagonist believed, and the love interest is morally grey in the way that makes romantic tension feel real rather than performative. The Sicilian setting gives it atmosphere that most romantasy doesn't try.
Yes. Yarros confirmed five books for the Empyrean series and Onyx Storm is structured as a third act that opens doors rather than closing them. The ending answers some questions that have been building since Fourth Wing but introduces new stakes for books four and five that are significant. Check our Empyrean series guide for release dates on the remaining books.
Do I need to read Fourth Wing and Iron Flame first?
Absolutely. Onyx Storm picks up directly after Iron Flame with no recap, and the new character dynamics in book three only work if you understand the full history of relationships built across the first two books. Start with Fourth Wing and read in order.
Which Maas series is most similar to the Empyrean books?
It depends what you loved most. For the romantasy romance structure, ACOTAR — particularly A Court of Mist and Fury — is the closest match. For a darker, more adult tone, Crescent City. For the military fantasy elements and a heroine with expanding powers, Throne of Glass. All three are worth reading once you've finished Onyx Storm.
What's the best book to read between Onyx Storm and book four?
A Court of Wings and Ruin is the best structural match: it's a third book in a romantasy series where the romance hits its most complicated point and the war goes continent-wide. Reading it between Onyx Storm and book four will feel familiar in the best possible way. If you've already read ACOTAR, try The Way of Kings for something that operates at an even larger scale.