From Bulbapedia, the community-driven Pokémon encyclopedia.
Whiscash Pond (Japanese: ナマズンのいけ Namazun Pond) is an area in Pokémon Mystery Dungeon: Red Rescue Team and Blue Rescue Team, to the north of Pokémon Square. Its main inhabitant is Whiscash, who tells stories to the player. He is the first to tell the Pokémon of the Curse of Ninetales. Once the player has stopped a meteor from destroying the world, an area called Luminous Cave appears in the center of the pond, where Pokémon can evolve if they are a high enough level, have an evolution stone in their possession if their IQ is high enough, etc.