Princess Kauril of Tarishah leads a double life. A decades old regency bars her from her empty throne until she bears an heir. To avoid power-seeking suitors, she becomes “Falcon,” an agent of Queen Sabrina of Fayette. Sabryna’s [Is this the same character who was spelling her name with an "i" three words earlier?] husband, King Jurriaan, is kept ignorant of Falcon’s true identity.
Prince Karsh of Sabbatus, a nation of warriors, escapes his murderous half-siblings and changes his name to Mordent. [Okay, I can tell already we're going to need a chart to keep up with this.
I recommend including this chart with the synopsis if you want anyone to get past those first four sentences.]
The battle for supremacy decimates Sabbatus. Mordent uses magic to manipulate Jurriaan into ceding control over Tarishah [Why doesn't he just use magic to manipulate his murderous half-siblings into their graves?] [How does the king of Fayette have any control over Tarishah to cede?] which allows Mordent to drain its coffers to revitalize Sabbatus. [Coffers. They're always being filled or drained, but no one knows what they are.]
The story begins as [Man, I hate it when I'm thoroughly confused, and then I find out the story hasn't even begun yet.] Sabryna, mortally ill, pleads with Falcon to resume life as the Princess and choose Jurriaan as her consort. [This is when the story begins? After Falcon is in Fayette?] Feeling obligated to Sabryna but unwilling to abandon the life she has created, Falcon has a clandestine affair with him and becomes his informant. [I feel obligated to Sabryna, so I'll screw her husband on the sly.]
Mordent discovers Falcon is Kauril and courts her. Jurriaan rebuffs Falcon’s counsel while Mordent enthralls her. ["Enthralls" meaning "enchants" or "enslaves"?] His planned seduction threatens her affair with Jurriaan and her freedom. Wounded in an altercation with Mordent, she flees Fayette.
Falcon discovers evidence implicating Jurriaan and Mordent in a scheme to plunder Tarishah. She scours the countryside to find proof to exonerate them. [One of them rebuffed her counsel, the other wounded her, and she's going out of her way to exonerate them? If I suspected they were plundering my coffers, I'd be looking for proof that implicates them.] A tax collector and a band of Sabbat soldiers reach the town of Ozapfelh before she does. [Why is she going there?] They seize most of its wealth. The villagers give Falcon one month to overt [overt?] an uprising by uncovering the culprit. [The culprit? It's the tax collector and the band of Sabbat soldiers. Took me three seconds; and Falcon has a month? Now if you mean who's behind the culprits, Falcon found that evidence at the beginning of this paragraph.] [I don't see an uprising by some villagers as a big threat anyway.]
Circumstantial evidence incriminates Mordent but her month is over. She accuses him of treason. His compulsion spell goes awry and she rejects his marriage proposal. [Marry you? A magician who can't even cast a decent compulsion spell? I don't think so.] Mordent then coerces Jurriaan to dismiss the charge.
Falcon unsuccessfully attempts to persuade Jurriaan to revoke Mordent’s power over Tarishah despite the acquittal. As she is leaving Jurriaan’s suites Mordent arrives. He chases her but she evades him. [Can Mordent do anything right? He's the Inspector Clouseau of evil sorcerers.]
In Ozapfelh cries of war threaten to drown saner voices. Falcon convinces them to take a more surreptitious approach, looting the tithe train and leaving the authorized tithe. [What are you talking about now? Wait, I know, you're talking about Brother Cornelius's Tiiiiiiiiiiiiiiiithe Train.] She hopes to delay a confrontation long enough to bear an heir and end the regency. [Bearing an heir doesn't get the Ozapfelhian villagers' wealth back, and even if it does, you don't bear an heir overnight. Are they supposed to rob the tithe train for the next nine months?] Falcon embraces the Princess’s duties even though she can’t reclaim her title.
If the princess wants to avoid suitors, she could just hide out in Sabryna's castle instead of becoming Sabryna's "agent." You might mention that she would rather be an agent than a queen.
The dynamic among the kingdoms isn't clear. Mordent is from Sabbatus, yet (according to the query submitted earlier) he's the Administrator of the Regency--in Tarishah. Kauril accuses Mordent of treason against Tarishah, but the charge is dismissed by Jurriaan, the king of Fayette. Mordent asks the king of Fayette to cede to him control of Tarishah. Are these three separate kingdoms, each with its own ruler? One could get the impression Tarishah is a province of Fayette.
This sounds like an 800-word synopsis that was reduced to 400, not by eliminating the least important events, but by keeping everything and eliminating the elaboration/explanations. It's an outline; a list. Throw in all the names, and places, and the reader's eyes are quickly glazing over. These seem to be the main plot points:
Barred from assuming the throne of Tarishah until she bears an heir, Princess Kauril flees her power-hungry suitors and takes up residence in Fayette. There she becomes Falcon!, an agent of the mortally ill Queen Sabryna.
The evil sorcerer Mordent, whose land has been decimated by his half-siblings' campaign for power, plots with Fayette's King Jurriaan to drain the coffers of Tarishah in Kauril's absence.
Falcon learns of Mordent's treachery and returns to Tarishah where she tries to get knocked up so she can legally have all her enemies tortured and killed.
Now, develop each of these ideas with specific information, but without adding new people, places, aliases, etc.