As far as henchmen goes. There was one idea i planed to use to explain random encounters in a video game. Instances of the number 666 (known by some as the number of the beast) appearing in some digital form (like on a computer, or a calculator etc) Would either act as a medium for some sort of supernatural force to manifest in our world or produce a gateway for them. I think this concept could work if the big bad we're dealing with is supernatural in nature. (or if we're dealing with a human capable of taping into these supernatural elements at will) I guess from here theres two directions we could go in. What comes out of the portals or manifests are the henchmen and with time they can eventually evolve into a bigger monster (the monster of the week if you will, sorta like the worms in kabuto). Or it could be that the monster manifests and is able to generate the henchmen from there.