The Dwelling of Ekhidna (Book Five of The Shape Shifter Chronicles) by Lauren Jankowski
The home of the guardians, the Meadows, has always been a place of peace and safety, untouched by the ongoing war against the Grenich Corporation. But that could only last so long.
During the guardians’ autumn celebration, a bomb goes off, shattering the Meadows tranquility. In the aftermath of a tragedy, a deadly virus is released that afflicts only healers. The only cure to the virus is hidden in the Seelie Court, in a location that only one knows: Eris, a legendary trickster, locked away in the dungeons of the Pearl Castle for her crimes against the peoples of Earth. When the Four are forced into a temporary alliance with the unpredictable Eris, their journey becomes more perilous than anyone expected.