Nightbirds (Armstrong)

2.

"The Nightbirds were once their city's best-kept secret, but now the secret's out. What's more, they can do feats of magic no one has seen in centuries. They're like the Fyrebirds of old: the powerful women who once moved mountains, parted seas, and led armies. Some say that when four join together, they become a force that shakes the earth and sends magic rippling through it. It does seem as if something has awoken in Eudea, but the four girls responsible...