During its development, it was known as Type: Full prior to the project's failure.
Type: Null is a chimeric-looking quadruped Pokemon 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.
Type: Null evolves into Silvally when levels up with high Friendship.
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.
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.
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".