Warehouse Chief Klump:
You can obtain red gems from many evil creatures. Get them by slaying the Tulben, Hames Orc Scout, Hames Orc Footman, Cursed Guardian, Hames Orc Overlord, Doom Scout, Dismal Pole, Doom Servant, Doom Archer, Doom Warrior, Blood Queen, Trives, Falibati, Doom Knight, Ghostly Warrior, Bloody Priest, Bloody Knight, Dark Guard, Death Agent, Black Shadow, Chimera Piece, Nonexistent Man, Forgotten Ancient People and Shaman of Ancient Times. To play the card game once, you'll need to bring me 50 red gems.