Warlock is book two in the Thirst for Power series, by Jason Halstead
There is more to life than power, wealth, and influence. Unfortunately, John's having a hard time proving what he knows to be true. His greatest power is also his greatest curse – a pact with a power Mistress with her own agenda. To be her champion and save his life, John must do her bidding. To save his soul, John must please her without destroying himself in the process.
The demoness Beytrixxa has charged John with expanding her influence in the western city-states of Kroth. One wayward daughter is the key. John must bring her into the fold no matter the cost to himself or his new friends.
For point of reference, the Thirst of Power series takes place several years after The Goblin Queen. It also involves some mature concepts, themes, and activities.
Keep an eye out for these other Thirst for Power books:
Book 1 - Enchanted
Book 2 - Warlock
Book 3 - Wizard (coming soon)