This book finally brings The Obsidian Trilogy, which began with The Outstretched Shadow and continued with To Light A Candle, to its conclusion. I would not recommend trying to read this volume by itself; the ongoing characters and their situations are for the most part not recapitulated.
The trilogy as a whole is a fairly impressive piece of worldbuilding. It is frustrating that some of the foundations are so terribly cliché, because by this volume we've really gotten past the fluffy pure unicorns, inscrutable elves, and over-the-top gratuitously evil demons. It's a complex story with exciting battles, interesting magic, and characters that manage to matter, and we're actually able to worry about whether the important characters will make it through or whether the Light will actually win. There are a couple of real surprises along the way, and it's actually satisfying when a couple of other things that were obviously coming come together.
I enjoyed it more than I had either of the first two volumes. It is a bit long, and you have to be able to tolerate the painful clichés long enough for the good stuff to build up. But I found it quite satisfying in the end. 9 out of 10.
** PLOT SUMMARY -- MASSIVE SPOILERS FOLLOW **
The book begins with the working of a great spell, as Idalia and the Wildmages, Kellen, Jermayan, and Cilarnen work together to scry through the wards surrounding Armethalieh. They discover Anigrel's true treachery, his plans to give Armethalieh to the Demons, and as they discover it they are caught by the Demon Queen Savilla, who attacks them through their scrying mirror. Kellen's will allows the power of the Wild Magic and Cilarnen's High Magick, with power from Jermayan and Ancaldar, to defeat the attack. Everyone who participates in the spell is drained and weak for days, but Savilla is also hurt by the backlash of her attack. The heroes have learned both the nature of the threat they face and the power of the combination of High Magick and Wild Magic. Cilarnen starts to make real progress in learning High Magick once he gets access to an Elven library. Jermayan and Ancaldar help to evacuate Lerkalpoldara, the northernmost Elven city, saving a few of the residents as the dark forces come to attack. The Demons don't fight fair; they spread plague and seek to divide the Allied forces by enticing them to defend their various homes. Kellen, truly coming into his own as a Knight-Mage and a Commander of Armies, manages to convince the elves that they have to stay together at all costs. It's made particularly difficult because the Elven King Andoreniel is gravely ill from the plague, in a coma, and not able to issue the necessary orders. Finally Idalia is able to get to Sentarshadeen and start to heal Andoreniel, and Kellen is given the authority to do what needs to be done. He encounters the missing enclave of Shadowed Elves at Halacira, a cavern complex he was planning to convert to a safe haven for the women and children of the Allies (so that the Allies would be willing to stay with the army). Thanks to his Knight-Mage powers, he is able to avoid having his force destroyed by a trap that floods the caverns. Idalia manages to perform a Summoning that brings a great power of the Light, the Starry Hunt, into the world. The arrival of the Starry Hunt disrupts the Demons and has them briefly disarrayed. Jermayan realizes that he could create a gate that would allow the greater part of the Allied army to join Kellen's force at Halacira, saving weeks of travel at this critical time when the Demons are recovering from the Starry Hunt's arrival, but only at a cost of all of his and Ancaldar's magic. He casts the spell, expecting to die, but the Starry Hunt intervenes and he and Ancaldar live, though they no longer have magic beyond their Bond. As the combined army under Kellen travels to Armethalieh, Cilarnen trains the unicorns to be the physical component of the spell to breach the wards around Armethalieh. Just before they reach Armethalieh, they realize that the Demon's plan is to sacrifice Lycaelon, the Arch-Mage (and incidentally Kellen and Idalia's father) at an ancient shrine to bring He Who Is, the creator of the Demons, into the world. They try to prevent the Demons from taking Lycaelon, but the Demons, through Anigrel, have tricked him into coming out of the city, and the Demons snatch him. Now Zyperis, the Demon Prince, tries to attack Armethalieh directly, while Idalia, Jermayan, and Cilarnen enter the city and work to convince the High Mages to cooperate in thwarting Savilla's plan. It is a very near thing; most of the Allied army is killed in the battle, along with the Armethalian mages who actually participate, but Idalia's spell actually works. Just as Savilla is completing the sacrifice, she exchanges herself for Lycaelon; she dies, but her sacrifice destroys the Demon spell and instead releases a great wave of Light magic into the world. That magic gives Kellen the power to kill Zyperis and Jermayan the power to kill Savilla, and all that's left is minor mopping up. Cilarnen becomes the new Arch-Mage and intends to make a lot of changes in Armethalieh. Idalia is honored by pretty much the entire world at her funeral in Sentarshadeen. Kellen's final duty is to lead an expedition to the Fortress of the Crowned Horns, where the elven queen, the young prince, and the other Elven children and pregnant women have been sheltered for the war. They are surprised to meet Jermayan and Ancaldar, who had disappeared after Idalia's death, and Jermayan leads Kellen into the fortress to show off the new Elven princess -- who has Idalia's eyes, a birthmark in the shape of the Elven betrothal pendant Jermayan finally gave to her just before her sacrifice, and Idalia's stubbornness. In just a few years -- not so long to an elf -- Jermayan and Idalia will be together after all. And finally, Kellen realizes that it's been more than a year and a day since he made his vow of celibacy (which allowed him to have the continued help of Shalkan, which was vital several times along the way), so he says good-bye to Shalkan and gets it on with Vestakia.