The Paris catacombs by Nomadic Matt
Ghasts-Gouls
Mostly based on myth
Ghoul myths originated in pre islamic Arabian religion, were they are described as humanoid with monster or demon like appearance who would consume flesh in graveyards. The word is derived from ghala which means "to seize". The myth was first brought into Europe in the book Vathek by William Beckford in 1786, were they were described the same way. Ghasts come from the H.P. Lovecraft story Dream quest of unknown Kadath. They were depicted as grey and repulsive humanoid creatures the size of a small horse that leaped on there hind legs like kangaroos, with oddly human faces missing foreheads and noses. They kept most of these traits for dungeons and dragons, but made ghasts smaller and ghouls have there past intertwined with elves, they also gained paralyzing claws that undead and elves were immune to.
In mythology
Arabian ghoul painting on a poem
Ghasts from Call of Cthulhu