- Action Survivor: Survivor is the keyword here, considering how many dangerous things there are in London Below.
- Can't Stay Normal: At the end of the book, Richard finally manages to regain his normal life back. However, he really can't get accustomed to it anymore, so he decides to return.
- Captain Obvious: Briefly becomes this during his initial confusion about the events going on around him.
- The Everyman: Richard really isn't anything special (though Serpentine recognizes him as a Hero).
- Genre Blindness: It takes him a few days to catch on, protesting that all these things are just Tube Stations!
- Good Samaritan: He's eager to help people. This is the reason why he was drawn into the events of London Below.
- Nice Job Breaking It, Hero: Nice job with the key, Richard.
- No Good Deed Goes Unpunished: Richard saves Door from dying on the street. And his reward? Being turned into an Unperson.
- Red Baron: By the end, he's known as The Warrior, for killing The Beast of London.
- Stranger in a Familiar Land: At the end of the book, when Richard finally managed to return back to the London Above, he finds it hard to fit in to a normal life again. Being unable to stand this, he manages to find a way back.
- Unfazed Everyman: After a day or so, he stops protesting impossible things and just starts accepting them, though he still doesn't really understand.
- Unkempt Beauty: He's described as having "a rumpled, just woken up look to him, which just made him more attractive"
- Unperson: After he had helped Door, no one could remember him. They also could barely notice him, unless Richard really tried to gain their attention. And even then it's really minimal.
Played by: Laura Fraser (Television), Natalie Dormer (Radio)
- Harbinger of Impending Doom: When she shows up on the street in front of Richard, bleeding profusely.
- Healing Factor: Her entire family has one to some degree. Not instant, but she recovers from a bad knife wound almost overnight.
- The Hero: Though Serpentine would disagree.
- Kaleidoscope Eyes: Her multicolored eyes are mentioned almost every time she's described. What color they actually are isn't really mentioned, as they seem to constantly be changing.
- Lethal Harmless Powers: She can open a door anywhere, like in your chest. Or to anywhere, like Hell.
- Living MacGuffin: Why do you think her family, with their ability to open doors anywhere, were hunted down?
- Magical Girlfriend: Though she and Richard would probably protest. If anything along those lines happens, it's after the story ends.
- Master of Unlocking: The whole family can open pretty much anything.
- Messy Hair: As a result of her travels through the sewer, it's unkempt to the point that Richard wasn't sure of her hair color.
- Mysterious Waif: Perhaps the ultimate example; an unnamed, oddly dressed girl appears from nowhere, bleeding and begging for help, which kicks off the adventure.
- Heart Is an Awesome Power: How useful would it be to open a door anywhere?
- The President's Daughter: Lord Portico was quite important and had dreams of uniting the Underground.
- Rummage Sale Reject: Her clothes are an odd mix of laces, velvets, and an oversized leather coat.
The Marquis de Carabas
- Animal Stereotypes: He's named for a character in Puss in Boots, which name he chose and styled himself after.
- Aristocrats Are Evil: He's certainly not a villainous character, but he's "a little dodgy in the same way the ocean is a little wet".
- Back from the Dead: About halfway through, he's tortured to death by Croup and Vandamar, but by the end he's been brought back thanks to his Soul Jar.
- Badass Longcoat: An iconic item on the Marquis. There's an entire story devoted to him getting it after it was taken from his dead body.
- Chessmaster Sidekick: Casually snags what turns out to be an important trinket from Portico's study; it's a totem of the Beast Islington gave him, pulls an impressive Thanatos Gambit on Croup and Vandamar, and is generally awesome.
- Crazy-Prepared: Everything from a Soul Jar to a convenient bit of fruitcake.
- Evil Chancellor: Richard explicitly compares him to a grand vizier.
- The Lancer: Door is noble, Richard is good (though helpless), the Marquis is just kind of a selfish prick.
- Loveable Rogue: He's more than willing to steal from the dead, but he's unquestionably on Door's side.
- Lovable Traitor: Played with. Is he? Isn't he?
- Meaningful Name: See above re: Puss in Boots.
- Only Mostly Dead: Thanks to his Soul Jar.
- Red Herring Mole: The bit in the middle when he meets with Croup and Vandamar is intended to make you think he might be their nameless employer.
- Sesquipedalian Loquaciousness: Though not nearly as bad as Croup, he's willing to talk, and talk fancy.
- The Smart Guy: He's the first one to figure out the plot, thanks to some clever gambits and some little bits and pieces the audience won't notice the first time around.
- Trickster Archetype: He wants to torment poor Richard, but Richard is just so naive and ignorant and helpless, he takes the fun out of it.
- You Owe Me: He deals in favors. Those he deals with usually regret it.
- Word of Gay: The book contains a number of clear hints, but it's confirmed by Gaiman saying that two of the characters in the story are gay.
Played by: Clive Russell (Television), David Schofield (Radio)
The Angel Islington
- Above Good and Evil: As revealed at the end.
- Ambiguous Gender: It's an angel, and no one objects to calling it "it".
- Big Bad: As we learn about two-thirds of the way through.
- Blondes Are Evil/Blond Guys Are Evil: Though not revealed until the end.
- Dissonant Serenity: Though it loses that serenity a few times.
- Dragged Off to Hell: Door sends him to the place furthest from Heaven at the end when she opens the door for him.
- Fallen Angel: After Atlantis.
- Faux Affably Evil: Because it's fairly polite, but doesn't really seem to get the point of the things humans care about.
- Light Is Not Good: It even lights up candles just by walking by them.
- Our Angels Are Different: To begin with, most don't live in subway stations. Or Islington.
- Psychopathic Man Child: At the end, it seems childishly confused when Door accuses it of killing her father, replying uncertainly "I didn't kill your father. I had him killed." Its temper tantrums also fit this trope.
- Villainous Breakdown: Oh boy. "They deserved it!"
- Your Heart's Desire: It agrees to help Door find who killed her parents, and get Richard home. And get Hunter that spear. And it does tell Door who killed her parents, and why. As for Richard, finding the way home was kind of incidental to its own goals, so, technically...
- Walking Spoiler: Because its fate is central to the Big Bad's motives.