Radiant

Evil creatures called Nemeses fall from the skies and the only ones who can fight them are Wizards--infected ones who survived a Nemesis's corruption. Seth, one of these survivors, vows not only to fight the Nemeses, but to find their mythical nest, Radiant, and destroy it! Descending into the chambers under Caislean Merlin, Seth confronts Diabal, a being with startling secrets! Seth's friend Melié, meanwhile, falls into the hands of two members...

"The war between the Inquisition’s army and the people of Cyfandir is drawing to a close, but the outcome is not at all certain. With both Seth and Myr falling down a path of darkness and destruction, neither friend nor foe may be spared from the potentially catastrophic consequences. Can their friends reach them and bring them back to their senses before it's too late?"--publisher's website.

"Evil creatures called Nemeses fall from the skies and the only ones who can fight them are Wizards--infected ones who survived a Nemesis's corruption. Seth, one of these survivors, vows not only to fight the Nemeses, but to find their mythical nest, Radiant, and destroy it! Heading to Bôme in order to retrieve the Nemeses their occasional ally Grimm stole from the Artemis Institute, Seth and his friends are separated while trying to ward off different...

"Relentlessly hunted by antagonists known as Domitors, Seth tries to fend off his pursuers and ends up discovering a new and surprising ability! Meanwhile, after being rescued by the alchemist Hurlä and the cheerfully oddball kids of the Droplet Gang, Seth’s friends Mélie and Ocoho set out to find him and their other missing friend, Doc. Unfortunately Doc’s lousy luck lets him down even more when he meets up with an old and not-at-all-welcome...