Four Ruined Realms by Mai Corland

A High-Stakes Assassin Romantic Fantasy (Broken Blades #2)

DELUXE LIMITED EDITION ―featuring gorgeous sprayed edges with stenciled artwork, as well as exclusive endpapers and special design features. 

The King of Yusan may be the greatest liar of them all.

His sister's ring is in his sights, and he will do anything to get what he wants. Even manipulating the five blades to steal it...

Bonded by a common enemy, then divided by deceit, the blades must rely on their skills to pull off King Joon's pursuit or risk his legendary wrath.

A foreign rule of law stands between them and Quilimar, the Queen of Khitan. Now they have one month to steal the powerful Golden Ring of the Dragon Lord. But that impossible task might be easier than trusting one another, even though their lives, their families, and the realms depend on it.

They can all agree on one thing: the king can't win. But can they beat him at his own game?

Because for the blades, this time it's not just personal, it's revenge. Lies may have torn them apart, but now vengeance will bring them together.

The Broken Blades series is best enjoyed in order.
Reading Order:
Book #1 Five Broken Blades
Book #2 Four Ruined Realms
Book #3 Three Shattered Souls