Nightmare Fuel / The Last Guardian

• At one point in the game the companions enter a water level where they have to dive through some tunnels. When diving through the second tunnel, it takes such a long time to swim through that the boy can't hold his breath anymore and unwillingly lets go of Trico who doesn't notice and keeps swimming till it disappears out of sight. Luckily the boy floats to a crack in the tunnel's ceiling and wakes up in a cave, but what if the conveniently placed crack hadn't been there? The boy would have surely drowned in that tunnel and Trico would have emerged on the other side without the boy, not knowing it just caused him to die. Then after the boy wakes up, he goes to look for his friend, and sees a Trico tail hanging over the edge of a cliff...
• Trico eating the Boy when hypnotized by the Ancient Relics. It's shocking to think that this creature that you befriended could turn on you so suddenly. Taken up to eleven when you watch the flashback, where Trico kidnaps the boy in the middle of the night and the other children and an old woman (presumably their caretaker) wake up to the sight of seeing nothing but his legs dangling out of the creature's mouth. They're afraid just seeing Trico at first, but then their cries become more panicked when the boy is swallowed completely, apparently having just been Eaten Alive.
  • The flashback scene is even worse since it seems as though the boy was hypnotized by the Trico, thus rendering him immobile as the creature picked him up and swallowed him. One can assume that the previous children abducted had the same thing happen to them.
• Near the end of the game, Trico is brutally assaulted by many others of his species, and one of them pulls his tail so hard, the end piece of it comes off.
• The Master of the Valley. An ancient Eldritch Abomination that takes the form of a sphere of black goo with bright green patterns on its surface. Stay near it too long, and it starts bombarding you with glyph control spells. The mirror causes it to shrink in on itself, but you then have to climb its cage - and it starts reaching for you through the bars. Not to mention that what, exactly, it is doing with all the children it collects is never revealed. It was strongly implied that the stuff in the barrels was basically made from the collected children, but Word of God Jossed this, so what it does with the children it was collecting remains a total unknown.