Pokemon Iron Treads - The monster was depicted in the Violet Book

The Violet Book, which will appear in Pokémon Violet, are records from an expedition, and they were written long, long ago. The expedition is said to have traversed an uncharted area of the Paldea region, but whether or not the accounts depicted in the books are true remains unclear. It seems Arven always carries a copy of one of the books with him.

The Monster Known as Iron Treads, was first shown in the final trailer. It is found with the Violet Book. You will be able to buy pokemon Iron Treads at 6kgold once the game comes out.