With Pride - Princes of the Blood, #2

When his sister falls ill, Kristof is ordered to assume a duty never meant for him: become the Duke of Stehlmore and marry a notorious Prince of the Blood. It is one of the oldest honors and duties undertaken by his family, but Kristof feels only resentment that he must leave behind all he knows to serve an arrogant half-demon. His resentment must be set aside, however, when evil is found lurking far too close to the castle-an evil that has many pieces, controlled by someone they cannot find and who always seems one step ahead of them.
Someone who seems to think that demons are little more than toys ...