Once you’ve acquired seven badges, try to enter the Viridian City Gym and you’ll be stopped by Brendan. He’ll take you to the Cerulean Cave as part of a mandatory story plot.

After Brendan and Ariana start battling, follow the path North.

You’ll come across some water. Use Surf here to follow the water without landing anywhere else.

At the very end of this path, you’ll see some stairs you can use to get back on land.

Now, you want to follow the path without taking any of the ladders you see on the way.

Eventually, at the end of this path, you’ll come across a ladder heading upstairs that’ll be on a separate platform. Use it to go to the Cerulean Cave’s maze area.

Now you want to walk left and then go down as soon as you can. Follow this path and you’ll get the choice to take one of three paths.

Follow the path to the very right.

Continue following the path, using Rock Smash to clear some rocks on the way, and you’ll eventually reach a ladder heading downstairs at the end of the path.

After going downstairs, you’ll see another ladder to your South.

As you approach it, you’ll be stopped by both Archer and Ariana who will challenge you one at a time, starting with Archer.

After defeating Archer, you’ll instantly be challenged by Ariana.

Ariana will give you the Mawilite after you defeat her.

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