I've got some nice ideas for the hook itself, and I know where I'm going to start the novel. The thing I'm struggling with is the hook in the query letter, or so to say, the short synopsis of the novel.

The setting is an 18th century fictional, earthlike world, and a country called Wellestria. The country freshly emerged from a civil war, through which a monarchy was reformed into a federation controlled by the nobility.

The first protagonist is an heir to family A (not going to flood this post with the names), an ancient and wealthy noble lineage.
His goal is to preserve his family and Wellestria, and to get revenge on family B due to an atrocity (will mention later).

The second protagonist is the youngest son in family B, not as wealthy and not ancient at all.
His goal is to preserve Wellestria, and prevent family A from plunging the country into chaos.

The third protagonist was the Federalists' leader in the civil war, from a less wealthy family.
Her goal is to preserve the Federation, to prevent family B from gaining too much power and to prevent family A from sparking another civil war.



The global conflict is a war declaration from a neighboring empire, Wellestria would need a unified answer in order to prevent an invasion, or even to prolong the defeat.
Protagonist 1 seeks to overthrow the federation and reunite Wellestria as a monarchy.
Protagonist 2 seeks to preserve the federation and make peace between the families in order to stand united against the enemy.
Protagonist 3 seeks to unite Wellestria through political means, as another empire under a talented leader (see Napoleon).

The local conflict is the one between the two families. The atrocity I mentioned sooner is a quarrel that happens in family A's castle, which results in it burning down, and most members family A dead.
Protagonist 1 seeks revenge with the remaining family members.
Protagonist 2's family (B) takes the opportunity and claims family A's lost power, thus becoming the greatest family with enormous political influence.
Protagonist 3 seeks a truce between the two families in order to gain their help against the invasion.

The third conflict is the inner conflict within protagonist 1 and 2. Both follow their families blindly. Should they honor the bloodline, or follow the rational path instead? Protagonist 3 has already decided, and seeks to convince the other two to be (more) rational.