While it is not known to evolve into or from any other Pokémon, Minior can change forms during battle, depending on its Ability and current HP.
Minior is a spherical Pokémon with two forms: one form with a rocky outer coating and the other with its core exposed. When it sheds its rocky coating its Core Form is the lightestRock-type Pokémon.
In its shielded form, Minior resembles a modestly sized rock. Its rocky exterior is formed by four large plates separated by two large cracks. The cracks encircle its body both horizontally and vertically. Five white spikes extend just above the rocky surface, giving it a star-shape. Two large, black spots on its front resemble eyes, and there is a third spot in the center of its back. Rings of dark brown triangles surround the holes its spikes protrude from and the spot on its back, pointing outward. One of the triangles surrounding the spot on its back is replaced with a small, brown dot. The eyespots have a half-ring of triangles resembling eyelashes. One eye has a small, brown dot in the corner. Even while apparently at rest, Minior tends to spin slowly in place.
In its core form, Minior loses its rocky shell and its body is exposed. The core is a bright, pastel color. Depending on the color of debris and food it absorbed and ate while in the stratosphere, Minior's core can be Red, Orange, Yellow, Green, Blue, Indigo, or Violet. A handful of darker triangles are also visible on its body in random places. Minior's eyes and mouth are formed from energy that floats in front of its body like a two-dimensional mask. The eyes are two large swirls and the mouth a smaller line. Its face tends to stay level regardless of how Minior spins the rest of its body.
Minior forms in the stratosphere from an aggregation of mutated nanoparticles, where it absorbs particulate matter from which it builds its core and shell. Eventually, this process makes it too heavy and it falls towards the surface of the planet. When its shell breaks from landing, Minior becomes lighter and capable of attacking quickly. However, it cannot survive for long with its core exposed, and will eventually die if not placed inside a Poké Ball quickly enough. The cute, pastel coloring of Minior's core form often inspires designers to use it as a motif for clothing and accessories. While in the ozone layer, it serves as food to stronger Pokémon. Places where Minior fall are few, Alola being one of them.
Minior is the only Pokémon whose forms all share the exact same Shiny appearance.
The Pokédex groups Minior under more colors than any other Pokémon, with a total of 6.
Minior is likely based on a meteor, which are colloquially known as "falling stars" or "shooting stars". The colors of its Core Form roughly correspond with those of a classic rainbow, or Roy G. Biv. Additionally, Minior's design may take inspiration from the Japanese star-shaped candy konpeitō.
Minior is likely derived from meteor, and may involve any mixture of the words mini, minor, junior, armor, ore, and core.