Return to Now, Book Three: Revolution in Anjhélius

The third installment of the epic Return to Now series plunges to the unexpected depths of the sea, to the troubled city of Anjhélius, weaving a tale of heroism, sacrifice, and the power of story.
The waters of the deep are not calm. The manta clan trembles on the verge of violent rebellion. And Nuala, leader of the rebels, has plans for the Prince. Seeking only a way to the mainland of the Now, Jack and Tija'l become embroiled in her treasonous plot, one that promises to save her people from oppression and tear her family apart.
"Who says you're supposed to be the hero, Jack" Nuala asked, surprised. "You are a part of this story, certainly. But a victory will require many heroes."

in which is chronicled:

The seige of the Picéan city of Anjhélius by the hoard;
the judgment of the Five regarding the Spheres of Power;
Jack and Tija'l's descent on giant manta rays to ancient ruins at the bottom of the sea;
their relationship with Nuala, warrior princess of the manta clan, and Nobidius, the fiery revolutionary;
the storming of the forbidden Basilica;
the sick secret behind Obsidia'nar's powers of illusion;
Nobidius' past encounter with Kra'akal;
the rebels undersea journey and desperate battle against the csyclythe and its consequences;
and the Spectacle on the eve of Samroun's Day that marks Obsidia'nar's rise to indomitable power.