He is created when Spawny combines a Rabbid, an inflatable rubber Boo, and a phonograph. His voice is provided by Augustin Chemelle. As per his name and theme, he sings a song for Mario and company before engaging in battle. The song is heard as part of the game's second trailer. hims the only Rabbid in game to communicate in a human language, instead of grunting and screaming. However, his song starts with several uses of the "Bwaah" sound, but in his own voice. He also makes these sounds throughout the battle itself.
In battle, the Phantom is initially immune to all attacks. To be able to damage him, Mario and co. must destroy the light fixtures beside him, disabling the spotlights focused on him; the Phantom becomes vulnerable once all active light fixtures are smashed. Each phase of the battle has one more light fixture to smash than the last, as well as giving the boss new Rabbid minions at the end of his first turn; Valkyries, Bucklers, and Peek-a-Boos. His main attack is a powerful operatic scream that acts like a rocket launcher weapon; it hits everyone within a radius for 40 HP and pushes them back. He can also activate a ghostly shield around him; the first hero to move within range becomes petrified, unable to take further action for their turn.
When defeated, the Phantom will throw a melodramatic, sobbing tantrum.