As to be expected with a story that doesn't shy away from darker themes, there's lots of nasty stuff encountered.
Nightmare Fuel in The Iron Heart of Man:
- The whole battle of Shanxi is full with Nightmare Fuel. Probably intentional to show war is no glorious affair. There's so much of it, that aside from the normal horrors of battle, and the splattering of people due to high power ammo, only the highlights can be listeted here:
- An Asari merc getting run over by an Apocalpyse tank being described in loving detail.
- The description of one horrifically crippled Asari - both hands and her lower jaw missing - and a dead Asari who took an incineration grenade directly in the face, thus burning her to a crisp.
- The attack on Desolas' command post with white phosphorous grenades. It's exactly as horrible as you would imagine it to be.
- It's frightening to read how Tela Vasir executes people indisciminatly, her feeling that everyone is guilty. Later learning she's indoctrinated actually gives this monstrousness a reasonable explanation.
- Tela Vasir's execution. There is no wonder why Kal'Reegar ran out and felt ready to hurl, considering the sheer sadism and brutalness Kai Leng exhibits.
- Harper's lovely description of the end result of indoctrination if applied for years. We don't see anything, but the description alone of someone being turned into a rabid animal with nothing left in his head is already bad enough.
- Jack is actually more frightening than in canon. When she's not on the job, she's a woman who loves to goof around with her co-workers and bemoan what a slave-driver their boss is. It's quite frightening to then see her torture people or go into battle. Smashing the skull of the Eclipse captain into paste with her boot is a reminder she takes her job very seriously.