Nightmare Fuel / Stardust (Arad)

• Twilight's first encounter with the Invaders: a Chryssalid massacring three people in front of her, then attacking her.
  • Twilight's response to it, crushing it into a pulp (they literally had to vacuum pump it out of the crater) with her telekinesis, is also this. In-Universe, even for Twilight herself.
• Twilight waking up in the X-Com containment unit, about to be "interrogated".
• Twilight's own nightmare where she repeats her killing of the Chryssalid, only it turns into Spike, plaintively asking why she's killed him.
• The Overseer Ethereal hallucination's Breaking Speeches in Broken are absolutely terrifying.
• Vahlen's Freudian Excuse as to why she is distrustful of Twilight: Her brother and niece were brutally massacred by Chryssalids, and she was on the phone to listen to it all.

Mente Materia

• Discord's choice of methodology for killing a Muton Berserker that makes the mistake of attacking him whilst he is distracted by the efforts of feeling Celestia trying to undo her Discord-induced bindings, meaning he can't bother with his usual tricks and games. He distends his jaws until they fill the entire street from top to bottom and left to right with rows of serrated fangs, then snaps it up when it charges right into them. All that's left is one severed leg, laying discarded in the alley.
• Chapter 11. It's Site Recon IN EQUESTRIA! Chryssalids everywhere! And it's as tense and horrifying as in the original.