The Central powers. Use machinery.

• A Mech By Any Other Name
• Humongous Mecha: Their war machines.
• More Dakka
• Steampunk: Clanker technology. Also, Diesel Punk.

His Serene Highness Prince Aleksandar Von Hohenburg

• Ace Pilot: Can pilot a Stormwalker easily - and at night, too. (Yeah, it's not a common skill. You can't SEE at night.)
• Cannot Tell a Lie: Up until the third book.
• Catch Phrase: Dummkopf!
• Celibate Hero: Alek started out as this because of his title.
• Cultured Badass: The "cultured" part is of no use on an airship, much to his annoyance.
• Effeminate Misogynistic Guy: Before he meets Lilit and gets some Character Development, anyway.
• Emo Teen: Lampshaded by Volger.
• Emperor Incognito
• Gratuitous German
• Lonely Rich Kid
• Noble Fugitive
• Red Oni, Blue Oni: The Blue Oni to Deryn's Red.
• Rich in Dollars, Poor in Sense
• Sheltered Aristocrat
• Shipper on Deck: For "Dylan"/Lilit.
• They Do: Abandons his claim to the throne to be with Deryn.
• Warrior Prince
• “Well Done Son” Guy: To Count Volger, whom he sees as a father.

Wildcount Ernst Volger

• Beta Couple: With Dr. Barlow.
• Fascinating Eyebrow
• Noble Fugitive
• Parental Substitute: Because Alek's parents are dead.
• Stern Teacher

Otto Klopp

Alek's mechaniks and Walker-piloting tutor.

• Ace Pilot: In his glory days.
• Cool Old Guy
• The Engineer
• Old Master

Corporal Hans Bauer

A Stormwalker gunner who joins Alek's group after the assassination of his father.

• Conveniently an Orphan: Bauer believes he was chosen for the mission because he had no family, which would make it easier for him to undertake a mission that would cause him to be labeled a traitor.

Hoffman

An engineer who helps Alek escape Austria-Hungary.

• The Engineer
• Conveniently an Orphan: Invoked. Like Bauer, he was chosen because he had no family left.

Lilit

• Action Girl
• Self-Made Orphan: She allows her father to sacrifice himself in order to destroy the German's Tesla cannon.

Zaven

Revolutionary leader of the CUP (Committee for Union and Progress).

• Cloudcuckoolander: Is thought of as being this, due to his cheery personality and belief in women's rights and equality, which would be considered unusual for 1914.
• Heroic Sacrifice: Zaven electrocutes himself in his mech to bring down the Tesla cannon, thus saving Deryn, Alek, and everyone aboard the Leviathan.

Nikola Tesla

A brilliant scientist and creator of Goliath, the world's first Weapon Of Mass Destruction.

• Mad Scientist
• Peace Through Superior Firepower: What he believes Goliath will bring.

The Entente powers. Use genetically modified animals.

• Attack Animal: The beasties.
• Bears Are Bad News: Russian fighting bears are taller than a house, and often ate their handlers (at least according to Mr. Rigby, the man in charge of the middies). In short, terrifying.
• Bio Punk
• Eldritch Abomination: What the Clankers see the Beasties, in particular the more horrific ones, as.
• Mix-and-Match Critters

Midshipman Deryn Sharp

• Action Girl: Blisters, is she ever.
• Attractive Bent Gender: Alek and Lilit both think this.
• Brave Scot
• Catch Phrase: "Barking spiders!"
• Fascinating Eyebrow
• Jackie Robinson Story: A minor example.
• The Lad-ette
• One of the Boys
• Plucky Middie
• Recursive Crossdressing: Wears a dress to the costume party in the Bonus Chapter.
• Red Oni, Blue Oni: The Red Oni to Alek's Blue.
• Sweet Polly Oliver: Has to disguise herself as "Dylan" Sharp so she can be in the Air Service.
• Tomboy
• Wholesome Crossdresser

Doctor Nora Barlow

• Beta Couple: With Volger, apparently.
• Dashingly Dapper Derby: Justified, as she's a boffin. The boffins wear bowlers.
• Historical Domain Character: Nora Barlow really lived, just... not like this.
• Hot Scientist
• Lady of Adventure
• No Celebrities Were Harmed
• Sesquipedalian Loquaciousness
  "Nascient Fixation sounded vaguely sinister, even if it was something baby ducks did."