The titular Jack is a Nightside dweller, but one with a unique quirk - instead of having his power bound to a specific location like everyone else, it is drawn from the shadow itself. This means that he is helpless in daylight or in pure darkness (since shadows are cast by the light), but enormously powerful once he finds any shadow to nest in.
This novella features examples of:
- Always Night: The Nightside, the half of the planet that is always facing away from the sun.
- Badass Boast: "I am Jack of Shadows! Shadowjack the Thief! I was beheaded in Igles and rose again in the Dung Pits of Glyve. I duped the lord of High Dudgeon in his keep and took his prize and pride. I am the prisoner in the jewel. I am the breaker of the Compact. I drank the blood of a vampire and ate a stone. So beware, all those who love the Lord of Bats or loathe me, for I have named myself Jack of Shadows!"
- Best Served Cold: Jack's revenge is a long time in coming.
- Dark Is Evil / Dark Is Not Evil: It's a relative thing. Jack is a pretty bad guy from the beginning, but there is a significant difference between the Jack of Shadows and the man they call "Jack of Evil".
- Demon Lords And Arch Devils: Jack finally deduces Morningstar's probable identity near the end of the book.
- Eternal Engine: There is a Machine at the Heart of the World (the purpose of which is to stop the Earth from rotating).
- Evil Overlord: A fair approximation of what Jack becomes.
- Exactly What It Says on the Tin: Certain Darksider names, such as "The Colonel Who Never Died," and "The Key That Was Lost."
- Good Smoking, Evil Smoking: Jack picks up the habit dayside.
- In the Hood: Jack wears one.
- Irony: Jack escapes his imprisonment by the Lord of Bats by forging his name on the Compact as current protector of the Shield. He notes that his opponent was the true guardian, and that if either of them had been minding their actual business, none of the plot would have happened.
- Impossible Task: Stealing the Hellflame for Evene's bride-price.
- Mayfly–December Romance: Jack and Rosalie. He promised to come back for her...and does—an unspecified number of decades later, long after she has grown old and begun to resent the fact.
- My God, What Have I Done?: Jack does realize that what he has done to Evene is unpardonable—but he fears to undo it, as being freed would drive her utterly insane.
- Naked on Revival: Anyone who is resurrected in the Dung Pits of Glyve.
- Perfectly Arranged Marriage: Evene to the Lord of Bats...eventually.
- Pet the Dog: Jack tries to do this with Rosie. He can't quite get the hang of it, however.
- Respawn Point: If anyone gets killed before exhausting his finite supply of lives, he is resurrected in the Dung Pits of Glyve at the east pole of the planet.
- Revenge: Becomes Jack's driving motive... in the interim.
- Roaring Rampage of Revenge: A low-key one when Jack finds of Rosalie's death.
- Shadow Walker: This is one of Jack's signature abilities.
- Speak of the Devil: Jack's powers include the ability to hear any person who speaks his name in shadow, and to continue listening in until they move out of it.
- Sue Donym: Jack of Shadows becomes "Professor John Shade" on the Dayside.
- Villain Protagonist: Jack.
