The Golden Diva is the final boss of Wario Land 4 and the main villain of said game. It can be fought only after unlocking the Golden Pyramid by defeating the other four bosses and then making it through the final level.
The Golden Diva first appears as a large, ghostly, floating masked woman who descends into the room in a ray of light before Wario and is attacked by the shapeshifting black cat that had been following Wario around the temple and helping with previous boss fights, but is unable to effect her in the slightest and the cat is disposed of, disappearing into the Golden Diva's face.
The Golden Diva then proceeds cover herself with with her fan and summons a collection of spinning masks which Wario has to throw at her fan in order to eventually destroy it. Once the fan is destroyed the Golden Diva attacks Wario using a collection of strange objects that must be thrown back at her to damage the boss, and as she takes more damage she becomes more and more demonic in appearance.
When her health reaches a critically low point the mask disappears completely, revealing the Diva's hideously monstrous true face as she goes into a frenzied attack, destroying portions of the floor and replacing them with spikes. After a few more hits, the monster vanishes into smoke except for its lips, which Wario destroys to free the cat and they escape from the collapsing temple with the treasure. During the game's ending the cat turns into a beautiful princess, having presumably been cursed by the temple and the Golden Diva, and gives Wario a kiss to thank him before ascending into heaven.