During its development, it was known as Type: Full prior to the project's failure.
Type: Null is a chimeric-looking quadruped Pokémon combining body parts from several different creatures. Its body is black and cat-like, with three-toed paws on its hind legs. However it has purple scales on its upper hips, its front legs are green and resemble an insect's or bird's, its tail is a blue forked fin with a grey membrane and a mane of grey fur hangs around its neck. Its head is mostly obscured by a metallic helmet with a ring resembling that of Arceus around the neck and a silver crest on the top. Its grey eyes are however visible through a pair of openings on the helmet.
Upon evolving into Silvally Type: Null's stats remain unchanged except for a slight increase in speed. However, it gains a much bigger movepool and can use a new ability.
The square cuts of hair on Type: Null's mane closely resemble those of Gladion who is Type: Null's trainer.
Type: Null's body resembles that of Umbreon and its tail is reminescent of Gyarados. It also has similar markings on its helmet to Zygarde 10% and a ring on its helmet is similar to Arceus. It's legs are also similar to those of Bug Pokemon, but it's feet resemble Grovyle's. It's crest is also similar to the crest feathers of Chatot or the tutu of Oricorio Pa'u Style.
Along with the Tapu Guardians and Mr. Mime, Type: Null is one of few Pokémon in the series to have a name with two words.
At first, when Type: Null was created, it was called as "Type: Full", meaning that it had the ability to change into different types like Arceus, until the experiment ended in failure.
This also refers that Type: Null is an artificial copy of Arceus.
Type: Null is one of three Pokemon created through scientific experiments by an evil organization, the other two being Mewtwo (created by Team Rocket) and Genesect (created by Team Plasma).
Type: Null may be based on a gryphon or a chimera. It also has many similarities to the dragon of the Ishtar Gate in the city of Babylon, such as the feline and dragon-like legs, dragon-like shape, and crest on its head. The ring surrounding its helmet resembles the one surrounding the torso of Arceus. It may also draw inspiration from Frankenstein's Monster, especially the bolts on either side of its head.
Type: Null's name is a mixture of type, and null; having no legal or binding force, or the value of Zero. It may also mean "no type" in contrast to "Type: Full" meaning "all types".