Eternatus is a gigantic, draconic alien Pokémon. Its body has a vaguely draconic shape and a skeletal appearance, and is largely dark violet with red highlights. Its main body and tail are long, thin, and resemble a spinal column, and it has four small, thin limbs ending in claws formed from spindly appendages attached at right angles. Its torso is formed from a cage of appendages resembling ribs, and inside is a glowing pink core that serves as Eternatus's energy source, absorbing energy to sustain it. The core can also project its absorbed energy into massive blasts. Its head is triangular in shape and has a pair of white, eye-like markings in the form of three connected circles, as well as a spindly lower jaw with several diamond-shaped teeth. Over its head is a translucent red film held between five long spikes extending toward its body's rear. It also has a pair of thin tendrils extending from its back, formed from numerous triangular segments. Eternatus's gigantic size makes it the tallest known Pokémon to ever exist.
If Eternatus absorbs a massive amount of energy at once, it will enter its Eternamax form, becoming far larger in size. Eternatus will also briefly enter this form when using its signature move Eternabeam. In this form, Eternatus's shape drastically changes. Its body becomes incredibly long and serpentine with most of its body forming a massive coil. Its entire body glows red in this form, and present at regular intervals across its length are black rings with spikes extending outward. Its back tendrils now curl around its main body. Its energy core rests at the center of the coil inside a cage of violet spikes. Eternatus's head takes on the form of a giant hand, with its fingers covered in black armor with spikes extending from the back of each segment. At the tip of each finger is a glowing pink eye.
Eternatus serves as the source of the Dynamax and Gigantamax phenomena in Galar due to its power leaking out in the form of Galar Particles following its defeat thousands of years ago by Zacian and Zamazenta. Pieces of its body imbued with its power rain down throughout Galar in the form of Wishing Pieces and Wishing Stars. When it is awake, Eternatus causes a phenomenon dubbed the Darkest Day, in which the massive quantities of Dynamax energy it unleashes causes Pokémon to Dynamax and rampage uncontrollably. It can also sometimes keep other Pokémon from Dynamaxing in its presence. Despite this connection to the phenomenon, it cannot be Dynamaxed itself, as its Eternamax form replaces that effect. Eternatus has been referred to as the Darkest Day.
As seen in the anime, Eternatus can use its energy core to target a Pokémon and force it to Dynamax or Gigantamax. The anime also elaborates upon its ability to block other Pokémon from Dynamaxing, depicting this power as Eternatus absorbing the Galar Particles in the area to make them unavailable for other Pokémon to use. It is also shown to be capable of forcibly reverting other Pokémon that have already Dynamaxed or Gigantamaxed through the same process. According to Rose in the anime, he was the one to have coined Eternatus’s name.
In its Eternamax form, Eternatus's power grows so immense that it causes a great storm of Dynamax energy around it, ripping holes in spacetime in the midst of the storm as it releases a virtually infinite amount of energy. Its tremendous power can even prevent opposing Pokémon from attacking it as it gathers energy.
Eternatus is an extraterrestrial Pokémon that came to Earth inside a meteor around 20,000 years ago.
Eternatus is the only known Pokémon capable of using Dynamax Cannon and Eternabeam.
- Eternatus is the only Pokémon with a base stat total of 690.
- Eternatus, in both of its forms, is the largest Pokémon overall in terms of height.
- Eternatus is the heaviest Poison- and Dragon-type Pokémon, and also the heaviest Pokémon overall introduced in Generation VIII.
- Eternatus is the only Poison-type Legendary Pokémon, excluding Arceus holding a Toxic Plate or Silvally holding a Poison Memory.
- Despite being unable to Dynamax, Eternatus is still capable of using Max Moves in its Eternamax form. This makes it the only non-Dynamax Pokémon that can use Max Moves.
- If the player has no Poké Balls when they are prompted to capture Eternatus, one will appear in their bag.
- It is also the first Legendary Pokémon that can be caught with any Poké Ball without the chance of failing.
- Eternamax Eternatus:
- Is tied with Blissey for the highest base HP stat of all Pokémon.
- Has the highest base Defense and Special Defense stats of all Pokémon.
- Has the highest base stat total of all Pokémon, with 1125.
- This also makes it the only Pokémon with a four-digit base stat total.
- Unlike other Pokémon in the anime, Eternatus is animated with 3D animation rather than 2D. It is the only Pokémon to do so.
- In the anime, Chairman Rose is the one who named Eternatus. It had previously shared its name with the Darkest Day event.
- Eternatus is the first Legendary Pokémon caught by a main character in the anime.
Eternatus' extraterrestrial nature and dragon-like appearance may be inspired by Uther Pendragon, King Arthur's father, who acquired his epithet and started using dragons on his standards after witnessing a dragon-shaped comet.
Its overall body shape resembles the skeletal remains of a dragon, with the ribcage shaped like a cannon and the head resembling that of the common nawab or "dragonhead" caterpillar.
Eternamax Eternatus resembles a hand crossed with a serpent. It may be based on the biblical Seven Headed Dragon that, in the Book of Revelation, throws one-third of all stars down to the Earth and is ultimately banished to Earth with the Nephilim, the Hebrew giants, an event that ultimately leads to the end of time. This account may also be the origin of the item Wishing Star and the Darkest Day. It may also be inspired by Ananta Shesha, the king of Nagas in Hindu mythology who is usually portrayed as a giant, coiled serpent with a thousand heads capable of spewing venom and fire, though some depictions simplify his appearance down to five heads. Shesha bears the deity Vishnu on its coils, similar to how Eternamax Eternatus's core is mounted atop its coiled body.
Eternatus may be derived from aether, eternal, aeternatus (Latin for immortalized), and Thanatus (Latin transliteration of Thanatos, the personification of death in Greek Mythology).
Mugendina may be a combination of 無限大 mugendai (infinity), ダイマックス Daimax (Dynamax) and possibly dynamic.