While it is not known to evolve into or from any other Pokémon, Zacian has a second form activated by giving it a Rusted Sword to hold. Its original form, Hero of Many Battles, will then become the dual-type Fairy/SteelCrowned Sword.
In its Hero of Many Battles form, Zacian is a large cyan lupine Pokémon with yellow eyes, a tan underside, a lean frame, a pink tail, and pink braids going down the side of its body. Two pink fringes of fur are present on its back. Battle scars are visible on its sides, and part of its left ear is missing.
It is believed to be either the elder sister or rival of Zamazenta. In the past, Zacian was feared and respected by the people of Galar. It worked together with the two ancient kings of the region to save it from Eternatus's Darkest Day. It can turn itself into a statue and slumber for eons. Zacian can also cast illusions, including a projection of itself, even as a statue. Additionally, it is capable of flying. Even though it is not capable of Dynamaxing, Zacian may still go berserk when bombarded by Dyanamax energy.
Zacian has two forms: Hero of Many Battles and Crowned Sword.
By absorbing metal particles, Zacian can change to its Crowned Sword form in battle. In its Crowned Sword form, the fringes of fur on its back become wing-like armor and its braids grow to resemble ribbons. Additionally, its head is covered by a golden helmet, and it carries a golden sword decorated to resemble Zacian's colors; when using the move Behemoth Blade, the armor on Zacian's back combines with the sword to increase its size and power.
Zacian can sheathe its sword when not in use by wrapping it with its mane. Crowned Sword is Zacian's true form, and it is at its full power in this form. According to legends, Zacian was known as the Fairy King's Sword, due to it being able to cut down anything in one strike, and it inspired awe in both its friends and foes. When together with Zamazenta in their Crowned forms, it can negate the power of Eternatus, even in its Eternamax state.
Zacian attacks with graceful, swift, and captivating movements, which have been compared to a dance. It unleashes quick slashes that cannot be seen by the naked eye; those struck by its sword will be cut down before they can feel the pain. The sword it holds in its mouth is really sharp and can cut through anything, even the thick scales of Dragon-type Pokémon, as if it were paper.
Zacian has two forms, Hero of Many Battles and Crowned Sword, which change its appearance, stats, type, and cry. Zacian will always be in its Hero of Many Battles form outside of battle. In battle, Zacian will be in its Crowned Sword form if it holds a Rusted Sword. In this form, Zacian gains Steel as a secondary type and has increased Attack and Speed. Additionally, if Zacian knows Iron Head, the move will be replaced with Behemoth Blade.
Moreover, it is tied with Mega Diancie for the highest base stat total of all Fairy-type Pokémon.
Crowned Sword Zacian is the heaviest Fairy-type Pokémon.
Despite being a gender unknown species, Zacian is referred to as Zamazenta's older sister in its English, Japanese, and ChinesePokédex entries; other-language versions use a gender-neutral word.
Zacian may be based on King Arthur's sword Excalibur. Its role as a warrior aiding a king may take inspiration on the Knights of the Round Table. In addition, its feminine nature may be a reference to the Lady of the Lake, the character responsible for giving King Arthur his sword, and its relationship with Zamazenta may allude to the relationship between King Arthur and his sister Morgan le Fay. It otherwise resembles a wolf, an animal once native to Great Britain and an important heraldic symbol for noble families during the Middle Ages. Its long, hanging blue fur resembles a caparison, a cloth covering usually worn by warhorses during the High Middle Ages.
The story of Zacian and Zamazenta retreating to the Slumbering Weald to recover from their wounds, and their return in the present day to save Galar, parallels the legend of King Arthur's messianic return.
Zacian's sword's ability to cut through anything, with Zamazenta's shield resisting any attack, could be an example of an irresistible force paradox. One of the most famous examples of this in folklore includes the Chinese tale of a peddler selling a spear and a shield with similar properties, only to be asked what would happen if the two items were to be used against one another. Another example tells of the Greek hunting hound Laelaps, which always caught its prey, being set upon Teumessian fox, which could never be caught, and had to be turned into constellations to prevent the paradox.
Additionally, the crescent shapes on its sword while using Behemoth Blade may reference Hati Hróðvitnisson, a wolf that chases after the Moon in Norse mythology.
The way in which "the" is transformed into "za" may be a reference to the substitution of the /ð/ phoneme ("th") to the /z/ phoneme, which is commonly made by speakers of languages which don't have the /θ/ phoneme originally, including Japanese. The substitution of "e" for "a" may also reflect the possible pronunciation of the "e" in "the" using the /ʌ/ or the /ə/ ("uh") phonemes, which may be represented by the "a" letter in many languages, including in the romanization of Japanese.