The Actaids are the four gods who keep order in the world. The Lord of Life keeps domain over all life on Earth. The King of Corpses dwells over death. [Does "dwell over" mean what you think it means?] The Baroness of Balance keeps order and harmony among the people. The Girl of Gifts gives humans their animal forms by their eighth birthday. [Change their name to The Actaids of Alliteration.] Rae, the half-dog, and his sister Arella, the half-coyote, break every law trying to survive while their father leads the rebellion against the weasel King Nalvero. [Is King Nalvero a weasel or half weasel? (I assume there are full weasels on this world.)] The two cause as much trouble for Nalvero’s soldiers, the Red Guards, as they can.
One day, however, they go too far. [Not clear what that means. What did they do?] The Red Guards trap them in a forest and set it on fire. The pair is rescued by a strange, young girl who resides in the forest. This stranger however, turns out to be more than she appears; she is the only human teenager on earth. [Wait, we're on Earth? And there's only one human teenager?] Rae and Arella plan to use the girl’s unique fighting skills and frightening appearance to help break their father out of jail. [The father is leading the rebellion from jail?] The young girl agrees to go, under the impression they know of someone who can help her obtain her animal form and become normal. Having lived alone in the forest for quite some time, she refuses to even give the pair her name. [I don't see the connection between having lived alone and refusing to give her name.] The group encounters Red Guards, a bounty hunter, curses, and several battles on their journey. Throughout their adventures [Meanwhile], King Nalvero consults with the King of Corpses through black magic and places numerous obstacles to stop the group on their mission. The King’s plans fail as the young girl begins to open up as she slowly bonds with Rae and Arella. [I don't see the connection between the plans failing and the slow bonding,] On the night before their father’s execution, [If Nalvero wanted to stop their mission, he should have moved the execution time up to immediately.] the group finds shelter with a canine tribe. The young girl even reveals her name -Ana. However, she quickly retracts her trust as she learns of Rae and Arella’s plan to use her. [Unfortunately, it's too late to retract the crucial revelation that her name is Ana.] The tribe is then captured by King Nalvero, who pretends to care for Ana as a part of a scheme devised by the King of Corpses. The whole setup turns out to be a trap as Nalvero reveals his malicious plan to kill them all. Just when Rae is about to be executed, [Rae? What about the father? Was he executed?] Ana realizes she does care about them and a great power surges up from deep inside her. [It is the Custodian of Colons.] She levels Nalvero’s army with just a wave of her hand. The trio realizes Ana’s great power and appearance must be a part of a well-known prophecy. They decide to travel together and push forward towards their destinies as a team. [What about the Dogs of Defense? Did they get killed? If so, change it. No one will want to read about dogs or even half-dogs being killed.]
I don't see the point of starting with the Actaids. First of all, only the King of Corpses gets mentioned as part of the plot, so he's the only one worth mentioning. Secondly, his role in the plot is minor, so even he isn't worth mentioning. And thirdly, the name "King of Corpses" sounds so silly that even if he were worth mentioning, mentioning him would kill your chances of selling the book. In fact, all the Actaids have silly deal-killing names. If they play a big role in the book, give them real names. We don't say God of Thunder, God of the Sky, God of the Sea. We say Thor, Uranus, Aquaman.
I realize that Superman often teams up with Batman, but that's just because he feels sorry for the guy. He doesn't need Batman. Likewise, if Ana can level armies with a wave of her hand, she doesn't need to be part of a trio with Dogbert and Wile E. You've given Ana unlimited power, without showing anything the other two can do beyond annoying the Red Guards.
You could condense this into the brief summary you include within your query letter. Once you get rid of the Actaids and the unnecessary information (e.g. The girl refuses to reveal her name. The girl reveals her name.) it should be about the right length for that. I recommend querying those who want you to include a synopsis only as a last resort. Better to focus your efforts on your book than on a synopsis.