Armor Is Useless: Averted in the case of Crosby, since he is an elite mook and has more armor than the average 33rd soldier, his armor protects him from blasts of magic, and from Count Wardes' attack.
Played straight in that while his armor does protect him from serious injury it still doesn't protect him from the effects of Louise's botched transmutation spell.
Artifact of Doom: The school's Staff of Destruction, ultimately subverted when it turns out to be a grenade launcher.
Ascended Extra: Some of the soldiers of the Damned 33rd from Spec Ops: The Line are named, referenced and fleshed out with their own backstories. And in the case of Konrad, The Radioman, a Little Bird crew, and a Heavy Trooper, also end up in Halkeginia.
'Joe the Sniper', the lone sniper who appears in the opening loading screen of the game, is given his own backstory in this fic. It turns out he is Alex Walker, Captain Walker's younger brother.
Badass Normal: Sgt. Crosby is a normal human non-mage that holds his own against mages in Halkeginia. Of course, being a soldier with modern weapons and a heavy dose of combat pragmatism helps.
Bottomless Magazines: averted, in the beginning Sgt. Crosby is careful to conserve his ammo since he has no means of replacing it. Then after he recovers the Staff of Destruction the trope is played straight when Osmond casts a replenishing spell on his magazine so that the bullets will replenish themselves.
Defrosting the Ice Queen: while not cold, the Weaver of Fate starts out very formal and mysterious when she first meets Crosby, the more she appears to him in dreams the more she warms up to him. By the second arc she is even flirting with him.
She also warms up to Lugo when he flirts with her.
She is most decidedly unimpressed by The Radioman's crude and lame pickup lines. But, since she threatened to turn him into a pony in Equestria, you could argue she's also gained a sense of humor since her introduction as a character.
She finds Pvt. Gobbi's ogling and awkward compliments endearing, this might have more to with him being a wide-eyed idealist and adorkable.
Gilligan Cut: Happens to Crosby after he finds out about Henrietta's secret mission and Guiche volunteering to tag along:
Crosby: "Your observations are noted. But my conditions are clear. I'll help in this mission, and even bring Louise and her familiar along, but (Guiche) stays behind. And that's final." (cut to the next day, with him leading the column, including Guiche) Crosby: (shaking his head) "I must be losing my edge."
And another member of the 33rd, Pvt. Pete Gobbi, ends up in another magical world.
Noodle Incident: Even though its alluded to in the flashbacks, as of yet we still don't know what happened to Walker in Kabul that traumatized him and paved the way for his undoing in Dubai.
The mutiny between the Exiles and the Damned which happened shortly after the 33rd's botched evacuation is alluded to, but not explained.
The Obi-Wan: The Weaver of Fate is this to Crosby, appearing to him in dreams to give him advice and encouragement on his quest to become the hero.
Papa Wolf: Crosby really doesn't like people abusing Saito, or threatening Louise.
Pet the Dog: Crosby's is nice to Saito pretty much on first meeting, as he reminds him of a fellow soldier from Dubai. Also we find out Saito is the same age as Crosby's estranged teenage son. No wonder he warmed up to Saito.
Remember when you played Chapter 10 Riggs and you laughed your ass off when the sticky grenade stuck to the soldier and he blew up spectacularly and you earned the achievement "The Human Factor"? He was Pete Gobbi, friend to the OC, and hasn't seen his baby girl since Christmas.