Pokémon Mystery Dungeon: Blue Rescue Team and Red Rescue Team/Western Cave

After recruiting Ho-Oh, you'll gain access to the game's most terrible dungeon: Western Cave.

The Dungeon
This dungeon is 99 floors high. Bring a tight belt, seetrap or reviver seeds, max. elixirs and bring a Pokémon who knows a move like heat wave.

Items

 * Reviver seed
 * Beauty scarf (key needed on the 59th floor)
 * keys
 * poke 10-500

Enemies
Western Cave is 97 floors of pure terror, consisting of Tyranitar, Alakazam, Bayleef and Venasaur. Then one more floor of Charizard, Blastoise and Miltank.

Boss Battle: Mewtwo
On the 99th floor is Mewtwo. He is weak to Dark and Ghost moves, so try to bring as many of those as possible, like Faint Attack, Bite, Curse (only if you are a Ghost type), and Night Shade. After defeating him, you can return and defeat him again. He has a recruitment rate of 99.9%. Congratulations, you have beaten the toughest section of the storyline!