His Serene Highness Prince Aleksandar Von Hohenberg
Alek for most people, Aleksandar is the only child of archduke Franz Ferdinand. Duchess Sophia, his mother, was enough of a commoner to exclude him from inheriting the Austro-Hungarian throne, but after his parents' assassination, he is taken away with the intent of eventually being returned to claim the throne once Emperor Franz Joseph, his grandfather dies.
"Well Done, Son" Guy: To Count Volger, whom he sees as something of a father (and certainly a mentor).
Wildcount Ernst Volger
A low-level noble, Volger is Alek's fencing tutor and his father's strongest supporter. After Franz Ferdinand's assassination he whisks Alek out of his family estate and becomes the de-facto leader of the fugitive group. He's trying to his best to protect Alek and his inheritance, stopping at next-to-nothing to achieve his goals.
Samus Is a Girl: When she first shadows Alek in an all-concealing outfit, he can't decide if she's male or female due to the combination of small size, agility, fearlessness, and strength. He decides that she must be a very acrobatic boy until Zaven says that she's his daughter.
A brilliant scientist and creator of Goliath, the world's first Weapon of Mass Destruction. Much like in Real Life, he's an idealist, and believes he has a moral obligation to end the war - whatever the cost.
Badass Boast: Again, much like in Real Life, about the capabilities of his Goliath superweapon. He claims it caused The Tunguska Event. It's believed that this was untrue, and that Tesla kept the remains of the meteorite in his luggage to hide this fact. Though it might be that his weapon summoned the meteorite in the first place.
Big Eater: He likes ordering lavish multi-course meals.
Foreshadowing: In his first scene we find out that to stop the warbears around his camp from starving, he fed them his airship, which is seen as quite horrible by everybody in the air force. He's explanation is that he couldn't stand seeing them suffer, so he let nature take its course. The entire situation foreshadows his plan to end the war.
Historical Villain Upgrade: The plans for his Death Ray bear fruit in this story. While he's not evil, it does make him extremely dangerous. He eventually decides to use it on Berlin, but Alek kills him and it's believed that it probably wouldn't have worked anyway.
The Entente powers. The most prominent here are Russia, France and and The British Empire. They use genetically modified animals, since Charles Darwin also discovered the "threads of life" (DNA) in this timeline. Darwinists consider themselves superior, as they use clean technology and, according to them, have no prejudices, in opposition to the so-called "monkey-Luddites", who believe that beasties are the works of Satan.
Eldritch Abomination: What the Clankers see the Beasties, in particular the more horrific ones, like the Krakens and Behemoth.
Alternate History Slang: At least as far as British English is concerned: Boffins (genetic engineers), beasties (genetically modified animals), curses like "barking spiders" and words like "clart" (crap).
Not So Different: They're no more saintly than the Clankers, or less likely to use dirty strategies. Also, while Clanker industry is seen as a great source of pollution, a few people (like Count Volger) point out that Darwinist fabricated animals have escaped into the wild many times and pose a danger to natural species.
Midshipman Deryn Sharp
Daughter of balloon flyer from the pre-Darwinist era, she always wanted to fly. However, as women are not permitted in the military, she disguises herself as a boy. With the aid of her brother Jaspert, she joins Air Force, posing as her nonexistent cousin Dylan Sharp and arrives on the Leviathan when one of her flight exams goes wrong.
Granddaughter of theCharles Darwin. She works at the London Zoological Society, which is More than Meets the Eye, and appears aboard the Leviathan on a mission to Turkey, which kickstarts most of the plot.
Dull SurpriseDeliberately; it's useful for a diplomat to appear in control when there are shocking developments. She admits that her ability to maintain it is quite strained when Deryn reveals her gender.
"Nascient Fixation sounded vaguely sinister, even if it was something baby ducks did."
What, Exactly, Is His Job?: She's the Head of the London Zoo, which seems to give her diplomatic authority and her suggestions have force with Captain Hobbes - Deryn finds it all quite puzzling until Barlow points out that being a "zookeeper" in a Darwinist society means a lot more than finding room for a tiger habitat.
The other midshipman left on the Leviathan after Doctor Barlow moved in, he wants to participate in war, but doesn't like beasties very much.
Butt Monkey: If something happens to a midshipman, this midshipman will be Newkirk.
Wild Card: He can be very helpful when it suits him, but above all, he works for the story.
Bovril is one of Nora Barlow's creations, the "Nycticebus perscitus" ("smart lemur") or Perspicacious Loris. It was originally supposed to be gift for the Sultan of the Ottoman Empire, but after hatching in Alek's presence, it bonds with the prince and accompanies him and Deryn.
Bond Creatures: It bonds with the first person it sees after hatching - Alek in this case - but has a strong bond with Deryn as well.
Cool Pet: It's a genetically modified lemur that specializes in attention and analysis.
Creepy Child: Bovril's actually very young (barely few months by the end of the story) and its speaking freaks Alek out.
Flawed Prototype: Nora considers it this, as the events of Leviathan may have damaged it - for example, it bonds with two people and acts oddly sometimes. Alek and Deryn consider it rather a Super Prototype, though.
Intelligent Gerbil: It's probably the most intelligent beastie of the crew (they're called "perspicacious" for a reason) and it talks, although it mostly repeats relevant words that it's previously heard.
Kill 'em All: Out of over ten loris that were travelling aboard Leviathan, only Bovril and Nora's survive to hatching.
Nonindicative Name: "Bovril" is type of Scottish meat. Lilit named it, explaining that it's the only British thing she likes.