Cydonia has theory which says that this pokemon is Ymir from Norse Mythology, which is also a enemy of Odin (which has two wolfs by his side and I suppose that in the game the wolfs legendaries represent Odin himself) and a giant. Ymir was killed by Odin and every part of his body was used to created natural elements such as terrain, water, etc...
In the pokemon world such a thing could be translate with this evil pokemon (Eternatus) becoming energy that resides in the terrain and gives pokemon the power to Dynamax (naturally become giants).
