SG-1 visits a planet under the rule of Sokar whose culture is derived from medieval Europe and heavily influenced by Christianity. The townspeople are terrorized by a "demon" — actually an Unas possessed by a Goa'uld in the service of Sokar — who demands human sacrifices, with the team becoming the most recent when the local religious leader charges them with being evil.
"Demons" provides examples of the following tropes:
- All There in the Manual: Supplemental materials and Word of God explain that the Canon's ring is actually a control/targetting device for a Goa'uld satellite in orbit, that is used to summon the "lightning".
- Body Surf: The Goa'uld jumps hosts from the Unas to the Canon, as the Unas body is dying after Simon shot it with a staff weapon.
- Bolt of Divine Retribution: The Canon invokes this with an Applied Phlebotinum ring that causes a bolt of energy to strike the ground and incapacitate the team. Carter likens it to getting hit by a zat blast. According to Word of God, it IS a zat blast, from a Goa'uld satellite in orbit, that the Canon's ring controls.
- Burn the Witch!: When the Canon accuses Teal'c of being a demon, he is put through the traditional 'tests' for witchcraft associated with the period. They don't actually get as far as the burning, as they believe him to have drowned after the dunking phase.
- Captain Obvious: When the team first approaches the town and sees the Christian imagery at the beginning of the episode:Carter: Looks like a church.O'Neill: And that would mean... what?Teal'c: That it is most likely Christians reside here, O'Neill.O'Neill: ...Thank you, Teal'c.
- Catchphrase Interruptus: Daniel gets about halfway through his "peaceful explorers from the planet earth" routine before he gets a door slammed in his face.O'Neill: Don't think they're buying it, Danny.
- Cement Shoes: Teal'c is chained to a rock and thrown into the lake to test whether he's a demon or not.
- Chained to a Rock: When the team first arrives, they free a young woman named Mary who has been chained to a podium in the middle of the town square to be a sacrifice for the "demon". Later, the entire team is accused of being demons after Teal'c's "resurrection", and they all end up chained to the same podium along with Mary.
- Dark Age Europe: The townspeople are descendants of Earth humans taken from medieval Europe, so naturally this trope is prevalent. Lampshaded somewhat with Daniel's explanation of the trepanning ritual, and O'Neill's reaction to it:Daniel: Well, they drill a hole in the person's head. By drilling a hole, the evil spirits are released, thus saving the person from eternal damnation.O'Neill: ..."Thus saving the person."Daniel: Well, they didn't call them the Dark Ages because it was dark.
- David vs. Goliath: Simon versus the Unas. The Canon actually draws an explicit comparison with the story of David and Goliath in the Bible.
- Devil, but No God: Discussed at the beginning of the episode. Since the culture of the planet is heavily influenced by Christianity, Daniel wonders whether the Goa'uld that brought them there in the first place could be impersonating the Abrahamic God. Teal'c states that he knows of no Goa'uld capable of displaying the necessary benevolence to fit the description, and it eventually turns out that the planet is ruled by Sokar, who impersonates the Devil.
- Large Ham: The Canon.
- Last of His Kind: Subverted. O'Neill had been under the impression that the Unas they killed in "Thor's Hammer" was the only one, but it's revealed here that they're actually a species.
- Mark of the Beast: The first "proof" that Teal'c is a demon is offered when the Canon places a red-hot brand against the mark of Apophis on his forehead and he shows no pain. Daniel explains that one of the signs of witchcraft in medieval times was the "mark of the Devil", a mark somewhere on the body that was insensitive to pain.
- Morton's Fork: Carter describes the process of dunking Teal'c in the lake a "catch-22", since if he sinks he'll be proven innocent but he'll be dead anyway, while if he floats he'll be proven guilty and burned at the stake.
- No Good Deed Goes Unpunished: O'Neill laments the fact that every time the team tries to help the townspeople, they end up getting themselves in deeper and deeper trouble.O'Neill: Carter, if I ever get the urge to help anybody again, feel free to give me a swift kick.
O'Neill: Major, next time Daniel gets the urge to help someone, shoot him.
- Not Quite Dead: The Canon — and the rest of the team — believe Teal'c to be dead after he appears to drown in the lake. However, he later wakes up and states that he place himself in a deep state of kel-no-reem once he realized what would happen, so that his symbiote could sustain him while he was under the water.
- Our Demons Are Different: It's not a demon at all, it's an Unas possessed by a Goa'uld, but that doesn't make any difference to the townspeople given that they're terrorized by a giant, hideous lizard-creature with superhuman powers.
- Precision F-Strike: O'Neill calls the angry mob "sons of bitches" when they push Teal'c into the lake.
- Satan: Sokar is posing as such to the inhabitants of the planet, routinely demanding five human "sacrifices" that are actually to be taken as hosts.
- Screaming Woman: The women tending to Teal'c's "body" begin screaming hysterically when he suddenly sits up.
- Sinister Minister: The Canon. He claims he has no choice but to sacrifice people to Sokar, but he clearly enjoys the power it gives him and it's implied he's not above using it as an excuse to get rid of people he doesn't like.
- Unwanted Assistance: When O'Neill tries to tell Simon and Mary that the Unas isn't a demon, Daniel keeps providing "helpful" explanations as to why it wouldn't make that much difference to them.O'Neill: It's not a demon! ...It's demon-esque, I'll grant you, but it's just a big ugly creature.Daniel: (sotto voce) Who is in inhabited by a Goa'uld, which gives it great strength, intelligence and the ability to regenerate...O'Neill: Yes, it's a very smart, resilient creature...Daniel: (sotto voce) ...In the service of Sokar, who for all intents and purposes is Satan to these people.O'Neill: [giving him a pointed look] But it's not a demon.Daniel: (normal voice) No, it's... not a demon.
- Waking Up at the Morgue: Teal'c wakes up as he's being prepared for burial following his "drowning".
- Ye Olde Butcherede Englishe: Averted. O'Neill can barely recognize a sign written in Middle English as being English at all, and Daniel has to translate it for the rest of the team.