Boss Keys are crucial collectible items in Donkey Kong 64.
After his defeat in the events of Donkey Kong Country 3: Dixie Kong's Double Trouble! and Donkey Kong Land 3, King K. Rool plotted to destroy DK Island in retaliation. His first plan was to use a massive member of the Kremling Krew, K. Lumsy, to destroy the island. But K. Lumsy refused, not wanting to destroy an island filled with "cute little monkeys." K. Rool deemed him too soft to be a Kremling and locked him up in a small island attached to his base, in a massive cage held down by eight locks, where he was to stay until he toughened up. He distributed seven of the keys to his most fearsome henchmen, while keeping the eighth one in his lair.
After K. Rool's arrival at DK Island, and his theft of Donkey Kong's Golden Banana hoard and friends, Donkey Kong finds his way to K. Lumsy's island. The giant Kremling tells his story, and is overjoyed when Donkey Kong agrees to help him regain his freedom. He warns them of how dangerous it will be to get the keys, and stresses not to tell K. Rool, that it must be their secret.
Collecting the eight Boss Keys is crucial to completing the game. Each time K. Lumsy is brought closer to freedom, his dancing for joy causes the portal to the next level to open up. Once all eight keys are retrieved and the locks removed, K. Lumsy will reveal the way to the final battle with K. Rool.
Jungle Japes: Defeat Army Dillo.
Angry Aztec: Defeat Dogadon.
Frantic Factory: Defeat Mad Jack.
Gloomy Galleon: Defeat Puftoss.
Fungi Forest: Defeat Dogadon.
Crystal Caves: Defeat Army Dillo.
Creepy Castle: Defeat King Kut Out.
Hideout Helm: Reach the final door in K. Rool's lair with both the Rareware Coin and Nintendo Coin collected.