Pokémon Mystery Dungeon: Blue Rescue Team and Red Rescue Team/Mt. Faraway

Grab a key and get in once you have beaten all three fields. It's time to find the Mirage Pokémon. But before you do, you've got to face the final test: Mt. Faraway.

The Dungeon
On the 30th floor, you'll find a locked door. Use the Key to get the Friend Bow.

Enemies
You'll find an array of Pokémon here. The ones you don't need to worry about are the on around floors 1-20. After level 20 things start getting more difficult.

Boss Battle: Ho-Oh
Finally, the summit. The mirage Pokémon appears. You never suspected it. The High King Ho-Oh. He's not easy (after all, he is the High King). After beating him, return with the friend area Rainbow Peak and defeat him again (he has a recruitment chance of 99.9%).