The Vault Demons are a trio of magical creatures that are too powerful to be destroyed. To keep them from running on a rampage, they are sealed inside the Fengdu Vault of Demons, hence their name. They were accidently released by Jake in "Year of the Jake" in Season 2.
The Vault Demons look a lot like Dragons, but each one of them has different characteristics.
Blue DemonThe Blue Demon looks a lot like a Chinese Dragon. It has a flat nose, a long moustache, a pair of antlers on top of its head, and red eyes. It always keeps its mouth open, revealing four fangs at each corner that dent towards the outside. This demon has a very slender body, with black quill-like spikes coming out of its neck. It also has a pair of kite-like wings attached to its arms. It has four long fingers and toes on each hand and foot clawed with long, sharp nails.
Green DemonThe Green Demon has a few similarities with the Blue Demon, but looks more like a Sumo wrestler than a true Dragon. It is potbellied and very muscular, with strips of blue cloth covering its lower part like shorts. It has a flat nose, pointy ears and black markings around its red eyes. It also has four fingers and toes on each of its hands and feet with sharp, black claws. It has black spikes running down its spine to the tip of its tail. Its wings are also attached to its arms, much like bats.
Purple DemonThe Purple Demon has a long and slim body with fur on top of its head and over its shoulders down to its chest. It has a bearded chin, a flat, almost human-like nose, long and pointy ears, and dark markings around its eyes. Its wings are shaped like sharp crescents, but aren't attached to its arms like the two other Demons. It has black spikes running down its spine and its tail forks into three separate ends. It only has two clawed fingers and toes on each of its hands and feet.
The three Vault Demons in general are very powerful and vicious creatures. All three of them can fly and have the same craving of spreading havoc al around them. However, each and one of them as a special power that only them possesses. The Purple Demon, for example, can extend its arms to incredible lengths to grab its prey from afar or toss them around. The Green Demon can also extend its pink burly tongue, which is strong enough to rip off a lanppost from its stand. The Blue Demon, on the other hand, shoots a flaming, purple shockwave out of its mouth, which burns its enemies.
Demise and Current StatusAt the end of "Year of the Jake", Jake manages to seal the three Demons back into the Fengdu Vault with some help from Fu Dog and his sister Haley. It is presumed that, like it had been before, the Fengdu Vault was placed inside Lao Shi's shop for safekeeping and to prevent a similar incident from occurring in the future. The Vault as well as its Demons are never mentioned again in the entire series.
- In China, there is an 1800 years old necropolis called Fengdu, the Ghost City. It is a small city modelled after the Chinese Hell of Taoist mythology with many demon depictions carved into rock.