V.E Schwab 
Shades of Magic 
The Steel Prince #3

Troubles arise for Prince Maxim when the notorious ship, the Iron Grip, docks at the Blood Coast. He discovers that in the past, Arisa, the Pirate Queen, has sadistically assaulted the local royal soldiery, leading to the demise of any troops that opposed her, and leaving only Isra alive. Maxim further learns that not only is Arisa a wielder of powerful forbidden bone magic, she is also Isra’s aunt. Under the cover of night, Isra moves alone to put an end to the Iron Grips moving into the town, but is stopped by Maxim. Together they venture into Verose in search of Arisa and her gang. In the Black Torch tavern, Arisa announces that she is holding a tournament in which the winner will earn a place on her ship, providing they first survive a match with her. In a moment of high tension, Isra loudly proclaims that she will join the tournament – for the sole reason of bringing Arisa to her knees.