Key #4: Don't kill the bandit (Name: Gope standing next at the crystal), later find him in the inn of Goznor.
Key #1: Tainted Grotto: B2, at a lake, stand under the skeleton that's right on the right of the lake, facing the lake, click X to get key.
Key #2: random zombies' drop item in Canonia.
Key #3: Catacombs (or Fox Tomb, where fighting with zombie dragon) located after the fight with Moric inside one of the coffins.
 "Burrito Bison: Launcha Libre"){kind=icon}
 "Strikeforce Kitty 2"){kind=icon}
 "The Last Door Ch.4 - Ancient Shadows"){kind=icon}
 "The Last Door - Chapter 3: The Four Witnesses"){kind=icon}
 "The Last Door - Chapter 2: Memories"){kind=icon}
 "JellyGo!"){kind=icon}
 "Epic Battle Fantasy 4"){kind=icon}
 "Monster Arena"){kind=icon}
 "Level Up!"){kind=icon}
 "Blocks With Letters On"){kind=icon}
 "Epic Battle Fantasy 2"){kind=icon}
 "MARDEK RPG: Chapter 2"){kind=icon}
 "Sprout"){kind=icon}