Altering Cave - Pokemon Fire Red and Leaf Green Guide - IGN

Found north of Sixth Island, this cave only have Zubats. However, if you have an E-reader connected to a gameboy advance using Japanese E-reader cards

Seafoam Islands - Pokemon Fire Red and Leaf Green Guide - IGN

One Island - Pokemon Fire Red and Leaf Green Guide - IGN

Route 2 - Pokemon Fire Red and Leaf Green Guide - IGN

Altering Cave - Pokémon FireRed #49

Seafoam Islands - Pokemon Fire Red and Leaf Green Guide - IGN

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Medali Gym (Normal) - Pokemon Scarlet and Violet Guide - IGN

Pokemon FireRed and LeafGreen :: Unknown Dungeon Guide

Pokemon FireRed and LeafGreen :: Full Walkthrough

Let's Play Pokemon Fire Red Part 83: Outcast Island/Altering Cave

Altering Cave - Bulbapedia, the community-driven Pokémon encyclopedia

PK3/WC3: Unreleased Altering Cave Pokémon - Unreleased/Beta PKM

PK3/WC3: Unreleased Altering Cave Pokémon - Unreleased/Beta PKM