Nightfell Games (The Dashkova Memoirs Book 5) by Thomas K. Carpenter

Katerina "Kat" Dashkova has become a potent sorceress using her magic to help Ben Franklin and the Transcendent Society in the fight against Russia and the Otherworld forces that threaten the civilized world.

But her powers are useless when a plague of monsters descends on Philadelphia, threatening to plunge America into chaos. As Kat searches for the source of the supernatural creatures, she encounters a mysterious benefactor offering favors for assistance, learns a dire secret that could doom the Society, and must face a contest against an unexpected foe from her past.