Using the Ancient communication stones, Vala takes control of Daniel's body from the Ori galaxy to warn the team that the Ori are preparing to send an armada of ships on a crusade into the Milky Way, and also reveals that she's mysteriously pregnant with a child said to be the "will of the Ori". Meanwhile, the Russian and Chinese governments want to negotiate with Landry for a new deal concerning control of the stargate.
First appearance of Tomin.
"Crusade" provides examples of the following tropes:
- All of the Other Reindeer: Vala claims that before being healed by the Prior, Tomin was shunned by all the other villagers because of his limp.
- Ascended Meme: Carter refers to the unstable vortex of an opening wormhole as the kawoosh, a term that was coined by fans long before this episode.
- Black and White Morality: According to Vala, this is more or less the worldview of the followers of Origin.Vala: It's all lies and propaganda as far as they're concerned: we're wrong, they're right; they're good, we're bad. We must worship the Ori or die, and they will fight until we are dead or they are. Period.
- The Bus Came Back: Vala reappears for the first time after her Heroic Sacrifice got her pulled into a black hole.
- Continuity Nod:
- Eating the Eye Candy/Female Gaze: Vala clearly enjoys being in the Men's Locker Room.
- Feet-First Introduction: The episode opens with a shot of an anonymous pair of combat boots stepping out of the elevator, before the camera pans up to reveal a very pregnant Vala with no explanation as to how she got there.
- Good Is Not Nice: Seevis, the leader of the anti-Ori resistance, has Vala chained to an altar for three days to prove her allegiance, and his plan to stop the Ori crusade involves an attack that would wipe out thousands of their followers, including innocent women and children. He also acts like a brute in his day job as the town administrator/barkeep in order to maintain his cover.
- Grand Theft Me: Vala takes control of Daniel's body using the communication stones in order to warn the team about the impending Ori invasion.
- Healing Hands: The Prior heals Tomin's limp, allowing him to join up as an Ori soldier.
- Hooker with a Heart of Gold: Vala's friend Denya, who turns out to be part of Seevis's resistance movement.
- Individuality Is Illegal: "Blessed are those who walk in unison."
- Knight Templar: Tomin is a genuinely nice guy who honestly believes he's doing the right thing, but unfortunately the "right thing" involves wiping out unbelievers.
- La Résistance: The underground anti-Ori movement led by Seevis, which Vala eventually joins until they're found out after Seevis's plan to sabotage the Ori fleet fails.
- Mistaken for Gay: Downplayed; Mitchell asks "Jackson" if there's anything he should know after Vala decides to check him out in the men's locker room at the beginning of the episode, before he's been filled in on the body-snatching situation.
- Mystical Pregnancy: Vala reveals that she's somehow gotten pregnant without doing any of the "necessary bits", and asks the team if they've ever heard of anything like that happened before.Mitchell: Well, there's one...Teal'c: Darth Vader.Vala: Really? How did that turn out?Mitchell: Actually, I was thinking of King Arthur.Carter: You were?
- Power Perversion Potential: Vala makes a quip about finally getting into Daniel's pants and seems to enjoy looking for Mitchell in the men's locker room, though it's downplayed since she doesn't really have time to do anything besides deliver her message.
- Secret Test of Character: A particularly cruel one; Seevis has Vala chained to an altar in the middle of the town square and denied food or water for three days in order to prove that she won't turn them in before revealing to her that he's part of the resistance.
- Sequel Hook: The last scene has the team heading out to search for Merlin's weapon, setting up the plot for the next episode.
- Shotgun Wedding: Vala marries Tomin in order to pass the baby off as his after inexplicably falling pregnant in a society that doesn't take too kindly to extramarital sex.
- That Came Out Wrong: The others insist that Vala move the story along and then act confused when she starts talking about needing Tomin to have sex with her, leading to this:Vala: Tomin and I got married...Carter: Whoa, married?Vala: Stay with me. I had no choice. I told you, he was very devout and there's no way he would have slept with me out of wedlock.(Beat)Mitchell: ...Okay, maybe we skipped ahead a little too far.Vala: (exasperated) Well, I tried to lay it out in order! ...Ooh, that's a bad choice of words.
- Who's Your Daddy?: Vala's unexpected pregnancy is an interesting twist on this trope. She later finds out that the Ori impregnated her in order to sneak their Dark Messiah into the Milky Way galaxy without causing a confrontation with the Ancients. Of course, when Vala initially tells SG-1 about the pregnancy they immediately assume she was just really promiscuous.Mitchell: And I ask this not 100% sure I want to know the answer: Whose baby is it?Vala: That's the thing: I don't know.Carter: As in...Vala: I swear, I did none of the necessary bits.
- Your Terrorists Are Our Freedom Fighters: Seevis's plan to sabotage the Ori crusade, which involves blowing up their ships and killing thousands of their innocents, would have looked an awful lot like terrorism from the perspective of the followers if it had actually worked. Vala openly struggles with it, and states outright that she doubts the team would have gone through with that kind of plan in his position.