How to obtain Eternatus in Kanto

Obtaining Eternatus

To obtain Eternatus, you must first obtain Zacian and Zamazenta. Zacian must be in its Crowned Sword form and Zamazenta in its Crowned Shield form. The items needed to activate these forms can be obtained from one of the stalls in Vermilion City.

Place Zacian in the first slot of your party and Zamazenta in the second. Fill the rest of the party with Poison-type Pokémon and go to Cerulean Cave to battle Eternatus.