The theme of grotesque, nightmarish video game enemies having once been human is something that developers seem to favour more and more in recent years. Somehow, knowing that these creatures were just like us at an earlier point in their existence has a way of hitting home for the player - both as a warning and, in some cases, a grim foreshadowing.
Many video game premises revolve around planes of reality that mankind can only guess at: Heaven, Hell, outer space, and even the purgatorial space between spaces. These realms are not meant for mortal men, so is it really surprising that any amount of contact with these places can turn you and your foes into something else entirely?
The unknown is perhaps the greatest source of inspiration for storytelling, from fantasy and sci-fi to the likes of Lovecraftian Horror. With endless possibilities comes endless dangers, and many who poke their noses where they shouldn't end up losing their humanity along the way.
And that's not good news for your character who has to deal with them.
10. Gengar - Pokémon Mystery Dungeon: Blue Rescue Team And Red Rescue Team (2006)
Even the most lighthearted entry on this list isn't without a deliciously dark twist - the kind the Pokémon Mystery Dungeon series is known for.
The player, a human that has turned into a Pokémon, is constantly goaded, inconvenienced, and eventually hunted down by Gengar and his client-swindling rescue team, Team Meanies. An unnatural 'imbalance' threatens the future of the entire Pokémon world, and Gengar is quick to come to the conclusion that this balance can be restored by getting rid of the human amongst them - i.e. you.
Forced to go on the run, not only does your rescue team disprove this theory (it's actually a meteor causing the imbalance), but you also uncover something very shocking about one of your pursuers.
Long ago, a cruel human boy touched the tail of a Ninetales, a fate that brings about a terrible curse. His Pokémon, a Gardevoir, selflessly chose to bear the curse in his place, and, instead of helping her, the boy fled without looking back. As punishment, he was turned into a Pokémon.
Gengar is that Pokémon.
The game's fascinating epilogue focusses on Gengar's attempts to rediscover his past life, the player helping him all the way despite how he treated them during the main story.