When sleeping in isolated villages, it’s prudent to shutter the windows and bar the doors, for goblins hunt the night. They crawl from their underground warrens and scramble forth in a gibbering, mumbling, mob. They overrun farmhouse, manor, and hamlet--and even strike the outskirts of cities--in their search for victims, whom they snatch up and carry back to their lairs.
What do the goblins do with the folk they carry off? It has long be supposed that goblins don't reproduce in the manner of most man-like creatures. All (or almost all) appear to be of the same sex, and while most goblins are small, scrawny and sickly green, there is an extreme degree of variability in form and features among members of the race.
The subterranean lairs of the goblins are always built within ruins of the time of Man. There strange machinery--hissing valves and wheezing pumps--surround large pools of viscous liquid. These are the goblin spawning pools. Their surfaces eddy and bubble and finally erupt with protean goblin life: here a hopping thing with one leg and one arm, there a headless giant (compared to his kin) with a slavering maw in his belly, and between a snickering thing with a goblin’s head on spider’s bloated body.
These neonates crawl from the muck and soon take their place with their fellows, apparently directed to tasks suited to their particular forms by their elders. Some tend the strange machinery, while others guard their den, but many are assigned to the raid gangs.
The gangs are essential, for the spawning pools need a substrate. Through the working of the machines and the fluid, and a process beyond the kin of anyone in the current age--including the goblins themselves--the unfortunate folk kidnapped are rendered in the pools into the stuff of more goblins.