The Last Council (Amulet #4)

Emily, Navin, and the crew arrive in the lost city of Cielis, but they soon realize it's not the utopia they expected to find. While Trellis and Luger are taken prisoner, Emily is forced to fight for her life in a series of tests that will determine who among the new generation of young Stonekeepers will join the Guardian Council.
Kazu Kibuishi's thrilling, NEW YORK TIMES bestselling series continues

Emily and her friends think they'll find the help they need in Cielis, but something isn't right. Streets that were once busy are deserted, and the townspeople who are left live in crippling fear. Emily is escorted to the Academy where she's expected to compete for a spot on the Guardian Council, the most powerful Stonekeepers. But as the number of competitors gets smaller and smaller, a terrible secret is slowly uncovered--a secret that, if left buried, means certain destruction of everything Emily fights for.