Pokémon TCG: Eternatus VMAX Premium Collection, Multicolor
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Despite this, 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. 
Pokémon TCG: Eternatus VMAX Premium Collection
Unlike other Pokémon in the anime, Eternatus is animated with 3D animation rather than 2D during the Sword and Shield arc. Currently, it is the only Pokémon to have this distinction. Infinite amounts of energy pour from this Pokémon's enlarged core, warping the surrounding space-time. It was inside a meteorite that fell 20,000 years ago. There seems to be a connection between this Pokémon and the Dynamax phenomenon.If all of your Pokémon in play are type, you can have up to 8 Pokémon on your Bench and you can't put non- Pokémon into play. (If this Ability stops working, discard Pokémon from your Bench until you have 5.)
Eternatus | Pokédex - The Official Pokémon Website Eternatus | Pokédex - The Official Pokémon Website
Its overall body shape resembles the skeletal remains of a European dragon, with the ribcage shaped like a cannon and the head resembling that of the common nawab or "dragonhead" caterpillar. During the climax of Pokémon Sword and Shield, the player confronts a powered-up version of Eternatus known as Eternamax Eternatus, which is fought in a semi-scripted Max Raid Battle and uses Max Moves like a Dynamaxed Pokémon.
This form is unobtainable, but briefly appeared in the move animation for Eternabeam prior to Generation IX. In Pokémon Sword and Shield, the move is not treated as a form change internally, and Eternatus's stats and form index value remain unchanged. If Shiny Eternatus uses this move, the Shiny version of its Eternamax form will not be registered in the player's Pokédex. However, a Shiny Eternamax Eternatus can be registered in Pokémon HOME's Pokédex by depositing Shiny Eternatus into HOME's storage, as it automatically registers both forms. If Eternatus absorbs a massive amount of energy at once, it will enter its Eternamax form, which is said to be its true appearance and is far larger. Eternatus will also briefly enter this form when using Eternabeam, another one of its signature moves.