Overall: 4 stars
The nitty gritty: This review presupposes that you are familiar with the FE core rules.
This is a big departure from the normal FE setting Aeturnum is an endless world city, set with a similar tone to the movie Dark City (if you haven't seen that, stop reading this and watch that) combined with a more lively, populated version of Dark Souls. The buildings are gothic, the outlook bleak, and several anachronistic elements set amidst cleqr evidence of the supernatural but with the supernatural being unknowable.
You play the role of the Tethered, humans who have bonded their souls to mystic lanterns/flame, gained extended (unlimited?) life spans, and are far more powerful than a human. None of which makes you a good person. Your charge is the shepherd humanity, to let them live their best lives admidst the threats that face them.
The good: the game simplifies several of the more complicated elements of the FE action system, adding in a momentum mechanic and a more flexible, clear set of action choices. The research mechanic is modified into becoming something a little less abstract, with a clear transactional element. Resources are more limited, which means that equipment carried is simplified.
The combat is much more lethal despite the increased power of the PCs, the challanges rise to the occasion, and as the game states, TPKs happen and should be expected. Death is just the betinning, and death of PCs is less about individual survival, and much more about the story goals of the combat. Dying to save 1,000 citizens of Aeturnum is clearly preferable to surviving, but letting 500 people die. The choices and dilemmas are well reinforced in the mechanics and tone, reinforcing story beats over raw combat.
Much of the artwork is fantastic.
The bad: If youre not a fan of tactical combat, this suplement does little to change things. Certain elements are still calculation heavy, and while the abstract systems exist, they have very little page count.
I think my biggest complaint is that the abstract "magic" system is not developed enough there are a couple pages, with brief explanations, but a couple examples would have gone a long way, as it is challanging to know what the creator envisioned. Minor typos, and some ok artwork in places, is a small detractor as well.
One element of the game that is hard on players and a GM is that as all the tools and pieces to make your equipment/attack spells/defenses are abstract pieces, there feels like a small hole in the setting. the equipment examples are great, and i would have liked to see more examples to flesh out the world.
The finish line: Ths certainly is a worthy addition to the fragged continuum, and if you ever wanted to play a Dark Souls rpg, you could do a lot worse.