Netherworld creatures are somewhat rare. This is not because there's any shortage of them in general, but rather because they have their own world and don't have to co-exist with humans if they don't want to.
Because the Netherworld is a separate dimension where only departed spirits and a few unlucky plot-centric humans end up, attitudes toward humans are very different there. Humans are considered more of a casual curiosity rather than a threat, and generally they find themselves treated just the same as the monsters. This still means they're quite likely to find themselves ripped apart and eaten, but only because of the natural order of the food chain rather than stubborn racism.
The Netherworld monsters that end up on Earth are usually only the weakest individuals of their kind, or sometimes the family of a monster whose company ended up relocating him to Earth; Apple in particular seems to be moving a lot of their personnel from the dark, slimy hell-pits from which they spawned. In either case, the monsters end up having to assimilate like all the native creatures.
- lantern-type monsters are known for their wizardry with knives.
- Zombie dragons are dragons whose usual breath weapon has been replaced by a corrosive mist that weakens its victims.
- A holy dragon is mostly known for actually NOT being evil - it's really rare in the Netherworld - but also having several magical powers.
- Tree golem, most well-known for NOT being able to run very fast.
Such monsters make excellent minion material, as they come from a world where haphazard violence and physical dominance is equivalent to the law. Most of them find even the small aspects of civilization in Earth's monster realm, such as a healthy respect for mortality and a wide selection of evil masters to choose from, a welcome boon from the chaotic drudgery of the Netherworld.