Doublade is a Pokémon composed of two swords. Each sword has a silver blade and a light gray hilt. Embedded in each hilt is a single, pink gem with a dark center that appears to be an eye. Attached to each pummel is a long, dark purple sash with a pink swirl pattern on the tip; the tip of the sashes split into four tassels. Doublade has two sheathes that are attached to a plaque. The sheathes are varying shades of brown with lines forming a triquetra pattern across the front. Near the top of each sheath are white teeth-like markings and rings with white centers that resemble eyes. A third ring extends onto the hilt and encircles the actual eye. The swords are able to communicate telepathically, and they use this ability to carry out complex attacks that are unstoppable even by those skilled at swordplay.
Doublade is tied with Aegislash for the highest base Defense of all Ghost-type Pokémon.
Doublade appears to be based conceptually on a pair of fully sentient, possessed magical swords. Considering the crossed swords and shield connecting the Pokémon together, it is probably based on a coat of arms. The fact that it started off as an ordinary sword as a Honedge may mean it could be based on the bushido mythos behind katana use; katanas possessed the user samurai's soul and attacked of its own free will. Visually, considering its build and hilt, Doublade seems to be based on a pair of either spatha, claymore, or possibly jian swords with their own scabbards, tassel-like prehensile limbs, and a shared shield connecting its scabbards together.
Doublade is a combination of double and blade.
Nidangill may be a combination of 二 ni (two), 断 dan (to sever), and 斬る kiru (to slay with a blade) or kill.