The Omega Children - The Agent of the Diaspora (Book 3)
Having succeeded in using the costumes to beat the Vahn at its game, the cousins must regroup after the deaths of those that supported them, though with Lexington in a coma she is their first priority. Suddenly their great instructions seem to hold little relevance.
The ancient doors into the Northern Hills have opened and Quixote discovers a civilisation that predates the current epoch - survivors of a previous age who have a vested interest in the costumes.
A man turns up claiming to be the last Agent of the Diaspora - an extremely obscure religion that gathers clothes from around the world, and tells them he should be wearing the bracelets.
Having earned the right to become prefects they set about trying to prove their ways are superior but face stiff resistance.
When the secret of the Southern Wasteland is discovered it changes everything and they use their powers to overcome the Vahn but with utterly disastrous consequences.