Duello - Book 1: The Medicine Masks

This will scratch your Game of Thrones itch.
...
Not since slavery itself was the United States so bitterly divided. A new issue now threatened to bring the American union to an end, once and for all.

The ensuing civil war resulted in a bleeding and battered nation, hopelessly fractured between two warring political parties - Unity and Fountain.

In an effort to bring the horror to an end, a mysterious foreign organization called the Sovereign Entity took control of what was left of the broken country and declared any and all violence strictly illegal - with one exception:

Each of the two rival political parties would select one anonymous sanctioned fighter to represent their interests.

The Unifier is the masked combatant who represents the Unity Party.

The Divider is his enemy, and the sworn champion of the Fountain Party.

When one is unmasked (dead or alive), another must take his place. The civil war would continue, but it was about to become colder, quieter, and a lot more personal.

Can a nation survive when every inch of it is ruled by two rival governments at the same time?

And what is The Medicine?