Conspirators’ Kingdom by Elyse Thomson

A disgraced villainess
Daughter of a dead traitor, lightning mage Taisiya and her surviving family live as pariahs. Taking on the new, unwanted role of diplomat for the isolated empire of Lethe gives the proud mage a chance to reverse her family’s misfortunes and regain her once-respected status. When arrivals from abroad include a handsome fae prince in need of a wife, she rushes to play matchmaker in return for riches.

A prince plotting a coup
Fae Prince Mereruka has kingly ambitions and six siblings who stand in his way. He is convinced the king’s command to marry a barbarian from a cursed land will either kill him, or worse, ruin his schemes. Yet meeting the ruthless, enterprising Taisiya gives him hope he has found his perfect—vicious—other half.

And a match made in hell…for everyone else
They strike a deal. Wealth and power for a bride. Except the price of failure is a favour—in whatever form he chooses. As they trade in innuendos and barbs, and bride candidates become scarce, Mereruka can hardly wait to see her fail in order to claim his favour—Taisiya’s hand in marriage. But it is her heart he must win if he hopes to survive his brother’s bloodthirsty court. Only a couple united in villainy can slay their way to the throne, and if he fails, their heads will roll.