The Family Pride. The Zero Enigma, #6

Six years ago, in the aftermath of the House War that nearly tore Shallot apart, Akin Rubén and Caitlyn Aguirre were betrothed in a bid to keep their rival families from returning to war.  Now, with both of them on the brink of maturity, that marriage is starting to loom.  The moment of choice, when they must decide to go through with the wedding or risk their families resuming their rivalry, is fast approaching.
And yet, all is not well in House Rubén.  Akin, the presumed Heir Primus, has many enemies, relatives who will do anything rather than see him succeed his father and link their families to their former rivals.  Powerful factions are gathering, ready to oppose the match by any means necessary.  Secrets from the past are being dug up and turned into weapons, just waiting to be launched.  In desperation, Lord Rubén - Akin's father - forces his son to enter the Challenge - a contest that will either prove his right to inherit or utterly destroy him.
But the Challenge is not quite what it seems ...