Cobalion is a stag-like Pokémon that is mainly aqua blue with eight black dots on it (four on each side). It has a light blue spiky tail and a white scruff of fluffy white fur covering its neck. Its feet are light blue with black tipped toes and a black line separating it from the aqua blue color. Its face is light blue and the top of its head is black while the rest of the head is aqua blue. It has orange eyes and two slightly jagged orange horns on the top of its head. It has orange spiked protrusions coming of its shoulders.
The first part of this Pokémon's name is a reference to a metal, Cobalt. This is also a reference to the fact this Pokémon is a Steel Type Pokémon, as well as the Pokémon's color; Cobalt, a shade of blue.
Cobalion along with Keldeo, Terrakion and Virizion seem to resemble Entei, Suicune, and Raikou by them all being able to walk on four legs, they are all legendary that can be used in the Gear Station, and they all seem to be tied together. Additionally, Cobalion is the same height as Entei, Terrakion is the same height as Raikou, and Virizion is the same height as Suicune.
Cobalion is the first Fighting-type legendary besides Arceus's Multitype in the Pokédex.
Cobalion is one of the main antagonists in Pokemon Rumble Blast. But later, turns out to be a hero as he was trying to save all the toys from Dark Rust.
Cobalion is likely based on a stag. Cobalion along with Keldeo, Terrakion and Virizion seem to be inspired by the Three Musketeers. Cobalion likely represents the character Athos from the novel The Three Musketeers, being the eldest and the leader of the group.
Cobalion might be a combination of the words "cobalt" (a type of metal, alluding to Cobalion's Steel-typing), "champion", and possibly "lion".