- The Western Keep (the Northwest Castle in the NES translation) is a desolate, ruined castle infested with bats in the middle of a deep forest and far from any town. Of course, the fact that there's a king in the throne room is a big tip-off that something's not right, but the implication alone is fairly sinister. Add to that the fact that the Marsh Cave (at least in the NES version) looks like ancient ruins with lots of valuable treasures deliberately hidden and locked away in its lowest levels, and it just looks like something very bad happened either to the ancestors of the people of Elfland or to a civilization that used to exist on the Elfland continent long ago. Given that the world of Final Fantasy I is in some ways After the End, this isn't a big leap to make.
- The Phantom Train's floor in Whisperwind Cove. It appears to be a village in some kind of alternate dimension where all the townsfolk have been transformed into various undead monsters and left to wander aimlessly in agonizing limbo, wondering what they've done to deserve such a fate and begging the party for help. Some of them don't even have that luxury. All of this while the game over music is playing.
Nightmare Fuel / Final Fantasy I